3 Step Guide To Overclock Your Core i3, i5, or i7 – Updated!

Latest edition of 3 step guides – September 7, 2010
Updated – February 26, 2010
Originally Published – January 25, 2010


So many users are searching around the net these days looking for advice on how to overclock their new systems but don’t know where to start.  To help everyone out, I decided a how-to guide was in order.  Searching around forums can be confusing and intimidating.  There are so many people willing to give advice, but who can you trust?  It’s hard to know, and I’ve seen many users sent on wild goose chases because they are following advice that doesn’t solve or even address their specific problem. I’ve also seen too much trial and error overclocking. What I will attempt to do is create a very simple three step guide to “one-size-fits-all” overclocking.

If you want to continue searching out other opinions, please consider each suggestion with caution. Some will undoubtedly be great, some will not.  There is one exception I would make for OC Forums- their “senior members”. These users are the ones with blue user names and blue stars.  They have been designated seniors based on their knowledge, experience, credentials, and contributions to the OCF community.  While not immune to error, these users generally know their stuff and can be trusted for good advice.


So, why should you listen to me? Well I’m not the end-all-be-all of overclocking, and I still learn new things every day. There are many people around OCF whom I highly regard for their knowledge and experience.  Having said that, I do have a bit experience overclocking computers successfully.  I’m a member of Team IRONMODS, and if you’d like to know more about the team and our accomplishments, please visit our website.  I’m also very active with the OCF benching team where I regularly participate in team events and online competitions with The Raptor Pit.


My goal here is for this overclocking guide to be useful for anyone with a newer Intel based system, i3, i5, i7, LGA1156 or LGA1366. With the same basic principles applying to all of them, the basic process doesn’t change whether you are planning to use your system as an everyday system, gaming or if you want to push the limits for a single benchmark.

This guide is also independent of your cooling system.  Whether you are using the stock Intel cooler or if you’re pushing to the extreme with liquid nitrogen, the basic steps remain the same.  One thing that is far too common is errors in mounting your cooling system, specifically the application of the thermal interface material (TIM).  If you don’t have much experience mounting a cooling apparatus, please refer to this excellent guide from Arctic Silver.

Determining methods for finding a stable overclock are highly controversial, and my suggestion is that we agree to disagree.  Everyone has their individual definition of a stable system, but when I refer to “stable” in this guide, I am referring to the stability of your selected “stability test.”  So for a power user or gamer who wants a reliable system that won’t ever crash due to an overclock pushed too far, you’d need to test with a program that will load all of the cores and threads applicable to your CPU, OCCT and Prime95 are two popular choices.  For a benching team member looking to squeeze every last MHz out of their chip for a 7 second SuperPI 1M run on liquid nitrogen cooling, SuperPI 1M would be the ideal test. In my examples below, my verbiage will obviously be geared more towards those running tests like Prime95.  Super PI 1M only takes a few seconds to complete, so when I say “run your stability test for five minutes” obviously you will have to tailor that instruction for your individual situation.

So with that in mind, we will attempt to isolate each portion of the system and overclock one piece at a time.  This may seem time consuming at first  glance, but rest assured this can potentially save you hours of troubleshooting and frustration. So go slow, and follow each step very carefully.


I also need to insert a disclaimer in here somewhere: I am not responsible for any bad things that happen to you or your computer as a result of you listening to my advice, nor is overclockers.com.  My goal is for this guide to be a safe overclocking guideline, but the burden for damaged hardware lies on the user performing the overclock!  Overclocking can damage hardware, the new 32nm CPUs seem to be particularly fragile.  Overclocking will also void your warranties.


This guide is written for you if you can get around in your system’s BIOS (basic input/output system). I cannot write this guide to cover the variety of BIOS represented.  If you are unfamiliar with your BIOS, search for more information regarding your specific motherboard.  Also, do not be afraid to get into your BIOS and have a look around, if you are ever concerned that you may have changed a setting erroneously, you can always load defaults, and start over.


The CPU micro-architecture has taken a huge leap from the 65nm Core to the new generation 45 and 32nm technology, it has brought many changes not only to the CPU’s but also to the chipset and motherboard design and functioning.  This is what make overclocking the i3/i5/i7 CPU’s so much different to their predecessor LGA 775 CPU’s.

The naming convention can be a bit confusing so let us look at the various CPU and their names:

First we have the Nehalem family which are all 45 nm CPU’s that included i7 1366 Bloomfield (i7-920 i7-975) and Lynnfield socket 1156 i5/i7 (i7-750 to i7-860). These are all quad cores with HT except for the i5 which has no HT.

Then the next family is Westmere which is essentially die shrink 32 nm CPU version of Nehalem and again you have the Clarkdale (socket 1156) in flavors of i5 and i3, both dual core processors with HT.

Gulftown which is the hex-core CPU’s and not available yet are also part of the Westmere family and features 6 physical cores with HT and will be socket 1366 only.

The above are all desktop chips, then to you get  the Arrandale and Clarksfield CPU’s which are mobile processors and the Gainstown which is the server equivalent of Bloomfield.

So, to summarize, we have socket LGA 1366 and LGA1156 which are essentially the board platforms that carry certain 45 and 32 nm CPU variants. Both platforms are DDR3 where the 1156 is dual channel only.

Intel Core i3, i5, and i7 CPU’s

The following are the different CPU’s available today on the market, except for the Gulftown hex cores which will be available late 3rd quarter of 2009.

Core i3 (Clarkdale – i3 530, 540)

The least expensive and least powerful choice are the Core i3 chips.  These are currently limited to two physical cores with both the i3 530/540 models supporting Intel® Hyper-Threading Technology. At this time, all i3 CPUs have two pieces of silicon (or dies) in the CPU. One contains the actual processing cores and all of the L1, L2, and L3 caches.  The second die contains a GPU (graphic processing unit) which is capable of outputting video without the use of a dedicated video card when used with an H55 or H57 based motherboard.  This second die also contains the PCIe controller and the dual channel IMC (Integrated Memory Controller).  The first die is manufactured on a 32nm process, the second die is manufactured on a 45nm process.  The two die are linked with the Intel QPI (Quick Path Interface). All i3 CPUs work only on LGA1156 based motherboards.

This is all very important to understand when attempting to overclock one of these CPUs, because you are actually in a constant juggle with overclocking both dies.  Why?  Because both dies derive their speed from the bclock (base clock) frequency.  Please understand that these new 32nm CPUs are more sensitive to high voltages, and have been known to fail even when core temperatures are well within “safe” limits.  Another major issue many users have been running into with overclocking these Clarkdale based CPUs is the IMC.  It is not nearly as powerful as the Lynnfield based CPUs, and many users are forced to run at slower memory speeds and timings to get stable.

Core i5 (Clarkdale -  i5 650, 660, 661, 670)

Dual core i5 CPUs (Clarkdale) are identical to the i3 CPUs, but also include Intel® Turbo Boost Technology. All i5 CPUs work only in LGA1156 based motherboards.

Core i5 (Lynnfield – 750)

Quad core i5 CPUs (Lynnfield) are identical to the low end i7 CPUs, the only exceptions being their lack of Intel® Hyper-Threading Technology, Intel® Virtualization Technology for Directed I/O (Intel® VT-d) and Intel® Trusted Execution Technology (Intel® TXT). All i5 CPUs work only in LGA1156 based motherboards.

Core i7 (Lynnfield – i7 860, 870)

The low end Core i7 (Lynnfield) are quad core CPUs made for LGA1156 based motherboards.  These CPUs are manufactured on the 45nm process.  They have dual channel IMCs and PCIe controllers built into the CPU die.  All i7 CPUs include Intel® Hyper-Threading Technology and Intel® Turbo Boost Technology. Lynnfield based CPUs are unique in that they do not have a QPI.  Because the PCIe and memory controllers are both integrated on the CPU die, there is no need for the QPI. They are known to have incredible IMCs and are capable of sustaining extreme memory bandwidth.

Core i7 (Bloomfield – i7 920, 940, 960, 965/975)

The mid range Core i7 (Nehalem) are quad core CPUs made for LGA1366 based motherboards.  These CPUs are manufactured on the 45nm process.  They have triple-channel IMCs built into the CPU die.  The PCIe controller is not part of the CPU, but is built into the chipset (on the motherboard), the CPU and chipset are linked with a QPI. All i7 CPUs include Intel® Hyper-Threading Technology and Intel® Turbo Boost Technology.

Core i7 (Gulftown – i7 980x)

The high end Core i7 (Gulftown) are hex (six) core CPUs made for LGA1366 based motherboards.  These CPUs are manufactured on the 32nm process.  They have triple channel IMCs built into the CPU die.  The PCIe controller is not part of the CPU, but is built into the chipset (on the motherboard), the CPU and chipset are linked with a QPI.  All i7 CPUs include Intel® Hyper-Threading Technology and Intel® Turbo Boost Technology.  Please understand that these new 32nm CPUs are more sensitive to high voltages, and have been known to fail even when core temperatures are well within “safe” limits.


Before we do anything, please start by going into your system’s BIOS, and load defaults, then save and exit.  Your machine will restart with default BIOS values.  Enter the BIOS again and disable all power saving features.  These include, but are not limited to; EIST, C1E, and all other C-states.  All other settings you can leave on auto for now. Although I would also recommend turning off any start-up slash screens, so that you can view your system’s post behavior.  Also, feel free to disable any “integrated peripherals” that will not be used (i.e. NICs, extra PATA/SATA controllers, legacy devices, etc).

If your motherboard fails to post after changing certain settings, you will have to locate and reset the CMOS. Resetting the CMOS restores the BIOS to its factory settings and is a “hard” reset of these settings. Become familiar with where the CMOS jumper or button is, you may need to use it a lot. Most of the time, a jumper is located near the battery on the motherboard. Most newer motherboards have a button in the same location and many may also have a button on the rear input/output panel for easy access when your motherboard is installed in a case.  If you need to reset the CMOS, please power off the system by flipping the switch on your power supply, or unplugging it completely for 10 sec, then activate the CMOS reset jumper/button for 10 sec.

Understanding CPU frequency

Before we go into how we overclock these CPU’s let us look at what determines how fast your CPU will run.  The following simple equation determines the clock speed of the CPU’s cores:

CPU Frequency = Base Clocks x Multiplier.

This is a biggest change from the old LGA 775 where FSB and multiplier determined the CPU speed.  The base clock is similar to the FSB but also has some key differences.  The base clock, also commonly spelled bclocks or bclk in forms, is the foundation around all the other frequencies discussed below.

The CPU speed of the new generation is not the only factor that determines how fast your PC will run, we have a few more definitions such as:

QPI Frequency – QPI or Quick Path interconnect is the Intel communication path upgrade from the older chipset and front side bus (FSB) communication path, so instead of the CPU communicating with the memory via the LGA 775 Northbridge, there is now a direct link (QPI) that increases efficiency.  QPI speeds are a function of base clocks, so as you increase your base clock your QPI speed will also increase, yielding an increase in not only communications speeds but also bandwidth, which leads to an increase in PC performance.

Uncore frequency – This sets the frequency of the on-die memory controller and the L3 cache.  Like CPU clock speed, dram speed, and QPI frequency, uncore is a multiple of Bclk. Uncore can be set independently of those other frequencies,  subject to certain stability limitations.  The uncore must be at least 2:1 of the DRAM speed otherwise you will not get a stable overclock, in fact your PC will not even boot if the ratio is not honored.  Increasing the uncore:dram ratio above 2:1 yields significant performance gains.  However, when the ratio reaches 3:1 it is not possible to maintain full stability.

Multiplier and Turbo – As mentioned above, the multiplier is the second factor in how CPU core speed is determined.  Now, not all CPU’s have the same multiplier, it is dependent on where the CPU is positioned in the price/performance curve of Intel’s range of CPUs.  Most of these come with a Turbo multiplier which is available if you enable the Speedstep option under the CPU settings.  Care should be taken when using the turbo as you may not be able to see the resultant frequency in the BIOS.  For instance, if your default multiplier of your CPU is 20 (i7-920) and you set your baseclock to 200 and you boot up with turbo enabled, you will leave the bios at 20 x 200 = 4 GHz, as soon as you enter your Operating system your turbo kicks in so you end up with 21 x 200 = 4.2 GHz.  Now if you also have C-State enabled, one CPU core will actually have access to a 22 multiplier which enable that core to run at 22 x 200 = 4.4 GHz.  You set your voltages expecting to run at 4 GHz and you cannot understand why you get a BSOD when you enter Windows, well, that is the reason, so take care when using turbo and C-State and adjust voltage to accommodate for the higher multipliers.

Important Voltages when Overclocking

There a few important voltages which you will need to manipulate while overclocking, below are the main ones.  Every motherboard Bios differ but all of them have the voltages as set out below.

  • V-Core – Directly related to the CPU frequency. As you increase the CPU frequency you would need incrementally increase the v-core as well.
  • QPI voltage/CPU Vtt – Increase in this voltage is necessary from the default as you increase your RAM speed, tighten the timings or increase QPI frequency.  It also helps to stabilize your overclock at higher base clocks.
  • VDIMM/DRAM – This is directly related to your RAM memory modules and increase will assist in stabilizing increase in Ram speeds.  Care should be taken not to increase this voltage more that 0.5 volts above your Vtt as you could cause permanent damage to your CPU.
  • IOH Core Voltage- This voltage aids when increasing base clocks above say 200.  In most cases leaving it at auto works best.
  • ICH Core Voltage- This voltage feeds the chip that regulates the communication from the peripherals to the CPU via the DMI. It is best to set this at auto.

Now that we have covered all the basics let us jump to what this article is all about…overclocking

Step 1)  Maximize Bclock Frequency

Isolate the bclock from the CPU

First you need to isolate the bclock and find its stable limit with your chosen cooling.  In order to isolate the bclock from the other components, the first thing you need to do is manually force a low multiplier for the CPU.  For example; at stock speed, an i5 750 runs on a 133MHz bclock and a x20 multiplier which results in its stock speed of 2660MHz (133×20).  Raising the bclock to 200 with the stock x20 multi would result in 4000MHz for the CPU, which you’re not quite ready for yet.  If you are shooting for a 200MHz bclock, then a safe choice for now might be a x12 multi, which would result in a CPU speed of 2400MHz if you were successful in reaching your 200MHz target bclock.  Doing this isolates the CPU from the bclock so you can focus on only bclock overclocking in this step. In some situations, x12 may not work, this is just an example though, so don’t be afraid to try other low multipliers if x12 doesn’t work.

Isolate the bclock from the memory

The fastest rated speed for memory on P55 with an i5 750 (for example) is DDR3-1333, which is a clock speed of 667MHz (dual data rate “DDR” doubles the bandwidth to 1333-like speed).  Just like the CPU, the memory receives its clock from the bclock via a multiplier, in this case x5 (133×5=667).  This is most often expressed in the BIOS as “2:10″.  If you were to overclock the bclock to 200MHz as described before, your memory would be running at 1000MHz (DDR3-2000), and beyond the specs of all but the most extreme memory.  To isolate the memory from the bclock, lower the memory multiplier to the lowest setting available, most likely 2:6.  If you were to reach your goal of 200MHz bclcok frequency, your memory would only be at 600MHz (DDR3-1200) and well within the capability of all but the worst DDR3 on the market.

Isolate the bclock from the iGPU (Clarkdale only)

Clarkdale CPUs include an iGPU (integrated Graphics Processing Unit).  If you are using an H55 or H57 based motherboard and the iGPU is enabled, please pay close attention to this section. Some early BIOS versions did not allow for iGPU clock speed adjustment, if you do not have this option in your BIOS, please update your BIOS to the most recent version.  This platform is still very new and immature, so this information may only be relevant for a short time.  However, at this current time, it appears as though the iGPU frequency setting in the BIOS is based on the default bclock frequency.  This means that an iGPU frequency that is set at 900MHz in the BIOS, will only actually be 900MHz if the bclock frequency is set to 133MHz, if the bclock frequency was raised by 25% to 166MHz, the actual iGPU frequency would also go up by 25% or 1125MHz.  This is a relatively simple concept to understand, except that YOU have to do the calculation, because the BIOS only reports the set frequency, not the actual frequency.  What makes things worse at this time is that there is no software monitoring utility that is capable of reading the actual iGPU frequency.

For now, it’s only important to isolate it as a variable from our overclocking process.  So, assuming your goal is 200MHz bclock frequency, which is a 50% overclock of the bclock frequency, you need to lower the set iGPU frequency to prevent its overclock during this process.  If the stock iGPU clock speed is 900MHz and we were to overclock it 50%, that would yield a 1350MHz actual iGPU frequency.  To bring 1350MHz back down to 900MHz we would need to reduce it by 33%.  So reduce the set iGPU frequency by 33% to 600MHz, with our stock bclock frequency, the actual iGPU frequency would also be 600MHz.  However, if you successfully reach your target 50% increase in bclock, your set iGPU frequency will yield an actual iGPU frequency of 900MHz, which is the iGPU’s stock speed.

Bclock voltages

For this step, there are only two voltages you should play with; VTT, and IOH.  IOH is easy, if you are running a single PCIe card (graphics card), give the IOH 1.3V, if you are running more than one PCIe graphics card, give it 1.35V.  VTT is the crucial voltage adjustment for achieving high bclock stability, which is also known as “CPU VTT”, “QPI/VTT”, or “QPI/DRAM”.  This is the voltage that is fed to the IMC (Integrated Memory Controller), and also has a major impact in overclocking the bclock. CPU VTT is the crucial voltage adjustment for achieving high bclock stability.  Stock values differ depending on platform and CPU, but as a rule of thumb LGA1366 likes a lot, P55 doesn’t need as much.

So, are you ready to start overclocking?  After entering your BIOS and lowering the CPU & MEM multipliers, go to the voltages section and raise your IOH to 1.3-1.35V and your CPU VTT to +0.2V.  Then restart your machine and go back into the BIOS, if your system fails to post and return to the BIOS, please re-read the last paragraph in the “prerequisites” section above, and start over.  If you still cannot get past this step, post in the forums for some specific help.

After you’ve restarted your system with your manually configured voltages and returned to the BIOS, I always recommend going to the temp/voltage monitoring section and checking the CPU temp.  If the temperature seems too high for your cooling, then shut the system down and double check that your cooling system is properly mounted, and making good contact.  Moving on, almost all systems should be able to achieve 150MHz bclock stability with stock voltages, so go to the bclock adjustment and change it from 133MHz to 150MHz.  Then save and exit and allow the system to reboot.  This time, allow the system to boot fully into the operating system.

Testing for highest stable bclock frequency

Once the operating system has fully loaded, start up RealTemp.  RealTemp should always be running while checking for stability of an overclocked system to ensure you do not overheat your CPU.  RealTemp shows your CPU’s core temperatures real-time, as well as the distance to TJ Max, my advice is to never exceed TJ Max.  Now start up CPU-Z, this will allow you to ensure that your overclocked settings have been properly applied, and that you are running at your desired speed.  Check both the CPU tab for the expected CPU frequency (should be 1800MHz at this point), and check the memory tab to ensure your memory is running at the proper speed (CPU-Z will show the frequency of the memory, not the DDR3 speed, it should be 450MHz at this point).  Now start up your selected test program, for example OCCT or Prime95.  Run the test for just a short amount of time, five minutes should be plenty.  Then reboot the system and return to the BIOS.

If the test ran without error, raise the bclock by 10MHz, reboot into your OS and run the test again.  If the test failed, raise the CPU VTT voltage by a small increment, reboot into your OS and run the test again.  You should be able to see where this is going, continue to raise bclock or CPU VTT voltage with a short test after each change, until you meet one of the following criteria:

  • You reach your desired bclock and successfully pass your stability test.
  • You reach your maximum safe CPU VTT voltage.
  • Raising the CPU VTT does not allow for additional stability.

* Note – there is a phenomena known as “bclock holes,” which seem to be less common now, but may still create confusion and frustration during this process.  But if you appear to have found your limit at a much lower speed than anticipated, please consider trying a step or two higher before continuing on.  A bclock hole causes system instability a particular bclock values, and going past them may allow you to regain stability.

Maximum safe CPU VTT

What is the maximum safe CPU VTT voltage?  Depends on a lot of things, but I feel like these are some basic conservative guidelines.  If you’re running the stock Intel heatsink and fan, I would not advise more than +0.2V, if you are running a high end air cooler I would not advise more than +0.3V on LGA1156 platforms, and no more than +0.4V on LGA1366 systems.  If you are running a high end custom water loop add another 0.05V to those values, and if you are using extreme forms of cooling then use whatever works best.  I’ve used up to 1.70V on an i7 920, and up to 1.55V with my i5 750 with extreme cooling.

Fine tuning

After you have met one of the criteria above, you should have a rough idea of your bclock limit, now it’s time to get a little more fine tuned.  Next, instead of 10MHz bclock changes, shift to 2MHz changes.  Then repeat the steps above and search for one of the three criteria again.  Also, ensure you check my note about “bclock holes” above, the same concept can be applied to this fine tuning step as well.

After you have found your highest stable speed to within 2MHz accuracy, lower the bclock by 2MHz and run your test again.  This time let it run for a full hour (for those of you testing with Super PI or similar, adjust for your situation).  If it passes the test  - Congratulations! – you have found your highest stable bclock frequency.

Step 2) Optimize Memory Frequency

DDR3 Basics

The next step is to find the limit of your memory.  To do this, first you need to look at the memory’s ratings.  DDR3 does not typically have a lot of overclocking headroom, so it’s important to start with stock settings.  In this example I will use some basic Crucial Ballistix PC3-12800 for my explanations.  This memory is rated for DDR3-1600 (800MHz) 8-8-8 24 1T with 1.65V.  Enter the BIOS and adjust your memory timings according to the manufactures rating, in this case 8-8-8 24 1T.  Now, consider your maximum/desired bclock frequency, 200MHz for example.  This memory has a stock speed of 800MHz, so a 2:8 ratio with a bclock of 200MHz would put us right at that stock speed of 800MHz.  You could set it and leave it there, but let’s say your maximum/desired bclock is not 200MHz.  For example, if you are actually trying to reach 210MHz.  If that were the case, the resulting memory frequency would be 840MHz (DDR3-1680).  So, similar to finding bclock stability above, we need to work our way up to the desired speed testing along the way. There is an exception to this section, and that is with Clarkdale base Core i3 and Core i5 CPUs.  They tend to have a very weak IMC, and are often times not capable of running memory even at their stock speed.  If you have a Clarkdale based CPU, you may have to sacrifice memory speed to attain a good CPU overclock.

Testing for highest stable memory frequency

Theoretically we should be able to run for at least an hour with the bclock at 200MHz and the memory multi at 2:8– why?  Because we already found out that this bclock speed is 1 hour stable, and we are not overclocking the memory yet.

However, the integrated memory controller (IMC) is powered by the CPU VTT voltage.  So under some circumstances, especially with the newer 32nm CPUs, you may not be stable with your memory even at stock speeds due to the overclock imposed on the IMC.  This is particularly true if you are running 4 DIMMS (P55/H55/H57), 6 DIMMS (X58), or 4GB DIMMS (P55/H55/H57/X58).  If this is the case keep the memory at stock speed, or even try dropping the memory clock multiplier to run at less than stock speed, and increase the CPU VTT voltage until you gain stability.  The newer 32nm CPUs seem to have particularly weak IMCs, and often will not run at the higher multipliers even if your memory is perfectly capable.

For testing memory, it is important that you take a break from whatever stability test you’ve been running, and use memtest86+ instead.  The easiest way is to download the .iso and burn it to disc.  Then configure your BIOS to load from your optical drive before the hard disk drive.  When you boot the system with the disc inserted, memtest86+ should start automatically, and immediately begin testing your memory.

But, our goal is to reach 210MHz bclock, which will result in 840MHz memory frequency.  In the BIOS, set your bclock to 202MHz, and your memory multi to 2:8, save settings and exit.  Allow memtest86+ to load and complete one entire loop.  A single loop can vary in length, and can take quite a while if you have a large amount of memory installed.  If the test ran without error, press Ctrl-Alt-Delete and enter your BIOS.  Raise the bclock by 2MHz and then save and exit.  If the test failed, raise the memory voltage by a smallest increment possible, and run the test again.  You should be able to see where this is going.  Continue to raise bclock or memory voltage until you meet one of the following criteria:

  • You reach your desired bclock and successfully pass a single loop of memtest86+.
  • You reach your maximum safe memory voltage.
  • Raising the memory voltage does not allow for additional stability.

Maximum safe memory voltage

What is the maximum safe memory voltage???  This is determined by two things: first, NEVER INCREASE THE MEMORY VOLTAGE MORE THAN +0.5V OF THE CPU VTT VALUE, second, how much do you enjoy killing your memory?  Throughout recent history, memory is probably the easiest component to damage with extra voltage.  While there are exceptions, most newer DDR3 memory modules do not need very much voltage to reach their practical limits.

Once you have satisfied one of the three criteria above, drop the bclock down 2MHz from your last stable setting, and see if memtest86+ will run through 2 or 3 loops without error.  If you wish to try to push your memory even further at this point, there is one more thing to try, and that is another bump in CPU VTT voltage.  This will possibly boost the capabilities of the IMC and give you a little more room to overclock the memory.  Otherwise - Congratulations! - you now have a relatively stable bclock frequency and memory frequency.

Step 3)  Stabilize CPU Frequency

Almost there

The last step in this guide is often the first step for users who run into problems and then troubleshoot for days afterward.  Leaving it to the last step makes the task much simpler.  You now have the following settings locked in; CPU VTT, IOH voltage, memory voltage, memory multiplier, and memory timings.  That means when we are looking for our highest CPU frequency, there are only two variables we need to play with: bclock and CPU voltage.

Right now your CPU multiplier should be very low, and your bclock should be quite high. If we move the CPU multiplier up right now, we would undoubtedly become very unstable, and unlikely to post.  The idea here is that if your bclock and memory are stable with the current settings, shifting the bclock down should not cause any instability.  So, change you bclock to 140MHz, and switch your CPU multi up to its maximum.  In our example i5 750, the normal maximum would be x20.  Intel’s Turbo feature allows for extra multipliers, and some BIOS will even allow for the higher multipliers to be forced.  It will not hurt to use this feature if you desire.  So with my example of the i5 750, with some BIOS, I would be able to lock in a multi of x21.

“Load-line calibration”

This actually goes by a few different names, but they are all meant as a means to reduce or prevent v-droop.  Most overclockers would advise you to enable this feature; I would only recommend it if you understand what it does.  It does typically allow for measurably higher overclocking, but at the cost of violating Intel’s design specs, and putting more stress on the CPU.  However, overclocking in its essence violates Intel’s design specs, so you’re not breaking any new ground with this feature.  I do not enable load-line calibration on my daily/gaming system.  But I always use it when I am trying to fine the absolute limit.  For more insight on the matter, refer to this excellent explanation at anandtech.com.

CPU Voltage

That brings us to the first thing that most users want to play with after powering up their new system for the first time: CPU voltage, aka “vcore”.  As you can see, this is actually one of the last things you should be changing.  I would recommend starting at a nice and easy 1.3V.  Surprisingly enough, many users are able to achieve very good overclocks with this modest amount of CPU voltage.

Testing for your highest stable CPU frequency

Once the operating system has fully loaded, start up RealTemp.  Now start up CPU-Z and verify that your overclocked settings have been properly applied, and that you are running at your desired CPU, bclock, and memory frequencies.  Now start up you selected test program, for example OCCT or Prime95.  Run the test for five minutes.  Then reboot and go back into the BIOS.

If the test ran without error, the raise the bclock by 10MHz, reboot into your OS and run the test again.  If the test failed, raise the CPU voltage by 0.025V, reboot into your OS and run the test again.  Continue to raise bclock or CPU voltage until you meet one of the following criteria:

  • You reach your desired bclock and successfully pass your test.
  • You reach your maximum safe CPU voltage.
  • Raising the CPU voltage does not allow for additional stability.

Maximum safe CPU voltage

For there is no maximum “safe” CPU voltage in my book.  My recommendation is to determine your maximum safe voltage based on your temperatures while running your stability test.  With stock air cooling this could be as low as 1.3V on some i7 CPUs while running OCCT.  Or it could be as high as 2.2V when attempting Super PI 1M with an i5 670 on liquid nitrogen.  Personally, I don’t like to see my load temperatures exceed 90C on air or water cooling, but it’s really up to you.

Is it stable?

So, once you find your highest CPU frequency by meeting one of the criteria above, lower the bclock by 5MHz, and run your selected stability test until you are satisfied.  If you are looking for a stable system as a power user or gamer, OCCT or Prime95 for six hours is more than sufficient in my testing, but you may run longer if you desire.  But for a true test of stability, I always like to play Crysis while encoding a Blu-Ray movie into an mpeg4 format.


Cooling your CPU, RAM and other heat generating components are key to the success and the level of how high you overclock your CPU.  Do not expect to reach the same level of CPU speeds on air or water cooling than your fellow bencher who is using liquid nitrogen.

Cooling not only plays a huge roll in reducing temperatures but is also determine how much voltages you can feed to your CPU before you damage or even kill it, especially with the 32nm Westmere CPU’s who are much more sensitive to voltages.  Electronic components behave differently under extreme cooling than under conventional cooling.

Use voltages in moderation and rather be safe than sorry, especially if you cool with conventional cooling such as air or water.

Final Words

Well, that about wraps it up.  Believe me, there is so much more to overclocking.  There are SO MANY settings you can continue to fiddle with, but this guide should get you 95% of the way in 5% off the time.  If you enjoy overclocking you system, I highly recommend joining one of the teams at OCForums.  If you like to push your system and you like to get competitive, look into joining one of our great folding teams, or the OCForums Benchmarking Team.  You’ll learn a lot and have a blast!

Please feel free to comment, and post any questions you have in the thread linked below where the great OCF community will help you out with any problems you may encounter!

Thanks to Brolloks and others for their help with this guide.


Tags: , , , , , , , , , , , , , , , ,


bda1967's Avatar
Nice job. We now have something permanent to direct people to about overclocking these cpu's.
EarthDog's Avatar
W00t! Changing the link in my sig now!!!! Great article!!!
sno.lcn's Avatar
Great job Miah

Haha oops thanks for pointing that out, got it fixed
bda1967's Avatar
Should this be a sticky in this forum?
This guide has been updated....please follow this link:
3 Step Guide Rev3.0
Austin3334's Avatar
thanks MIAHALLEN hopefully i can o'c by myself without having to post on here all the time.

georanma's Avatar
So awesome. Glad to see this come to fruition.
napynap's Avatar

Thank you for writing this. Now I have confidence to begin overclocking having some knowledge of why a value should be tweaked or not.

After reading that, I noticed it was posted today! (1/25/2010), and I immediately signed up to this forum..
Conumdrum's Avatar
Yea, it's awesomely done. Really will help a LOT of people.
Thanks for the feedback guys...I really hope it's helpful to a lot you you all
ripetros's Avatar
Very good HOW-To man. I just signed in because of you post. But i have a question. What about PLL and PCH for P55 chipset should we give them a small boost from the beginning?
Norcalsteve's Avatar
Excellent read! vote sticky!
qisoed's Avatar
great job MIAHALLEN now I have guide to pull y i3
reap3r's Avatar
Excellent guide, saves going around and googling for half decent help on how to overclock those i# CPUs.

+1 for sticky
bcsizemo's Avatar
That's what I'm talking about!
Thanks again guys!
No...as stated in the guide, these should be left on "auto"...Raising the PCH is a bad idea, and I've heard can burn HW pretty quick...I have not found it to help an OC at all. The PLL can even be lowered a bit
Deaks2's Avatar
Excellent article. I have not had much experience oc'ing since my A64 X2 rig was built a few years ago. In fact, I am in the market for a cheap little i3 530, and this guide will help out.
ripetros's Avatar
Thx man i will, i will lower them. I thought that because of high FClk i should give them a small volt. As for the PLL i read that in a review of other i5 testings that it is good over 200 clock to give the PLL +0.1 V. THx anyway i will lower mine.
Nebulous's Avatar
Extremely informative read! I vote icky sticky!
Brutal-Force's Avatar
I have used this guide, and I agree... it works!
WOW! It's great to hear all the positive responses, thanks again guys...spread the word
aoch88's Avatar
One question: Some people say that by increasing your VTT, it reduces your Vcore. In my case, it never happens. How true is this?
No true at all taken by itself...but I'd be interested in seeing this comment in the context in which it was originally stated
hokiealumnus's Avatar
Me too. I've never heard anything like that. Link?
Brolloks's Avatar

What you propably have heard that you could lower your v-core if you increase your Vtt slightly to stabilize your OC, but is does not happen automatically.
Dataman2's Avatar
start by going into your systems BIOS, and load defaults,

Whoa there. If somone is running ACHI and set's BIOS defaults won't it default to IDE?

Then they get Error Code



I know it's easy to go back into the BIOS and change it back to ACHI, but telling novice not to write down the setting BEFORE they change the BIOS is asking for trouble.

Of course if they never changed it to ACHI it's one of the 1st things they should do before the OS install.

Otherwise loved the writeup.

hokiealumnus's Avatar
IMHO, if someone is using ACHI and doesn't know to set it back prior to booting, they may want to consider learning more about their setup prior to overclocking.

I guarantee, at some point and some overclock, they're going to need to reset CMOS. Doing so will remove any ACHI setting. They'll need to know how to recover from that just as much as they would from setting defaults.

You are correct though, it will default to IDE.

Oh, and welcome to OCF!
Dataman2's Avatar
But a warning to write down your settings and make sure of the mode would be safe way to do it. Trust me someone will do this and blame the OC.

Telling them to start off with changing to "default" is just asking for trouble. Most of us don't need the guide. But this is for the person who is not experienced. That person will do this.

When I build a system the 1st thing I do is reset to Default, then Kill the Stupid Splash Screen on the BIOS, then the ACHI Mode if Sata.

I have seen too many people change the BIOS settings and not have a CLUE. A+ Classes, MCSE Classes, Network Classes etc.
Point taken DM...My thinking was inline with Hokie...that when I said "reset to default", hopefully the use would realise they may need to consider the context of their situation.

Anyhow, thanks for the feedback, I'll be working on a follow up shortly to address some of the suggestions I've recieved, and I'll definitely consider adding a note on this
Dataman2's Avatar
It will help that Sys Admin who thought of removing the MB screws with POWER ON and said


Snap, Crackle Pop. It don't work anymore. Give me another one please.
(Novell Class where they took everything apart for Practice, they just could not put them back together and functional).

One other thing to consider. When I build I go into BIOS and check the temps. Good way to make sure you have those STUPID Push Pins on right! Before I load OS or try to OC it. So many don't bother to check until they ask "Why is it running so HOT or keeps shutting down".

Also put in there something about "Never Flashing BIOS on OC System" unless you play Russian Roulette with S&W Model 410. Good way to make a brick out of running system.

But...uhhh I thought I included that step???.....<goes to check>.....yup, it's here:

Dataman2's Avatar
Must have scanned past it.

xtkxhom3r's Avatar
nice article man
ivwshane's Avatar

This is exactly what I needed. I've been out of the seen for so long that all these new terms in the bios totally threw me off!

Glad this has been helpful for you guys
HunterZ's Avatar
This is an interesting guide, but a lot of what you're talking about seems to be X58-specific and doesn't make any sense for a P55 user like me. It would be helpful if you could revise it to make more sense from and/or be more applicable to a P55 perspective, or else split it into two separate guides.

Just a few examples - please don't get hung up on just these:

- What the heck is IOH? There's no such thing in my EVGA E657 BIOS.

- Vcore is much more critical than VTT on P55. It really is! I run VTT at Auto but had to bump Vcore up significantly (but reasonably) to reach 4.2GHz on a Core i7 860.

- What about the 1.65V hard-limit for safe RAM voltage on P55? Your guide only says VTT for i5 can get as high as 1.55V but that RAM voltage can go up to 0.5V higher; if people take that to mean 2.05V for RAM on P55 (NO!) then they'll fry their hardware.
Brolloks's Avatar

Most of what is in this guide is applicable to the P55 platform, remember that the micro-architecture of the CPU's that go into the X58 boards are the same as those that go into the P55 boards, they all belong to the Nehalem (45nm) or Westmere (32nm die shrink of Nehalem) family. Bloomfield is X58 based and Lynnfield is P55 based and both is 45nm micro-architecture, they all have the memory controllers on the CPU die. The P55 CPU's also have base clocks and multis which determine the CPU speeds. Both have uncore and QPI speeds that are key to CPU performance.

Vtt, or also known as QPI voltage, is just as important on the P55 CPU's as it feeds the IMC (Internal memory controller) and aids in memory OC as well as higher base clock stability. Vtt should also be used with more care on the Westmere 32nm chips whereas the 45nm Nehalem CPU's can tolerate much more.

The 1.65 VDIMM limit is a myth really and has been disproved thousands of time over, as long as you keep your RAM voltage and VTT within 0.5v you will be good.

Please read the guide, use what works for you and adjust, that is how you learn, that is how we all learned, from the masters, then a few like Miahallen became a master himself
ihrsetrdr's Avatar
A good read, Miahallen- thanks for giving us[former] skt 775 guys a guide for this next breed of Intel processors.
hokiealumnus's Avatar
There's an update to this coming soon. Should be out next week. We'll let you know. Great improvements to an already quality guide.
Gillbot's Avatar
Nice, I can't wait to toy with my i3 530.
OC nub's Avatar
Thanks, Very nice guide, , I spent the afternoon playing around with this. It works very well on the P55 board. Max bclk on my P55A UD6 without going crazy on the VTT was 220. I did short LinX runs to test for stability, 10 passes to save time.
kkpudge7's Avatar
Awesome guide mia...

I was able to get 4Ghz (8hrs stable) without ht, and only 3.8ghz with ht only somewhat stable prior to this. Using this guide as a reference I'm now working towards 4.3Ghz HT stable. Breaking it up into sections like that is the key, you cant change a ton of settings at once because then you dont know why its failing.

Breaking it into sections allows for much easier trouble shooting. Keep up the good work man
hokiealumnus's Avatar
Bumpety Bump.

Update has been published folks...catch it here!
DreadCthulhu's Avatar
First of all I'd like to thank Miahallen for putting together this extensive guide, I think it's a step in the right direction for a lot of people like me who have absolutely 0 experience with overclocking.

One piece of feedback that I wanted to leave is that as an owner of an i5-750 running on a GIGABYTE GA-P55M-UD2 I found some of the variables mentioned in the guide to be missing or new ones to be present. If you're completely green like I am, it's be very helpful to know how those additional (or missing) variables relate to what's in the guide. Here's a couple of points that were unclear to me:

- The "Bclock voltages" section talk about an IOH voltage. On my p55 gigabyte there's no such thing, instead I have a CPU Vcore, a Dynamic VCore (DVID) and a QPI/VTT Voltage. The Vcore is mentioned at the end of the guide in step 3. Given that IOH appears not to exist in P55, do I just ignore the suggestion to raise it to 1.3-1.35?

- In the same section, and in the rest of the guide, you measure tweaks to the VTT in terms of +0.xV (where x is a number). What does that actually mean? Are you saying we should take the default value of the BIOS and increase that by +0.xV? I guess the confusing part is that in my menu there's the DVID variable which actually does have + and - 0.xV settings, so to me it's not clear whether you're asking to keep the VTT default and tweak the DVID, or if I should ignore the DVID and only increase the VTT.

Thanks for the feedback...glad it helped!
Thant was the idea Please post in the forums if you have questions that the guide does not address. We're here to help...great job so far, keep it up
Great feedback! Thanks!

This does not apply to all boards, as many lower end boards do not support extensive OCing features in the BIOS. Since you do not have the ability to tweak IOH, just pass that section. (the difference will be minor anyway, VTT voltage adjustments are the main factor in bclock OCing).

- VTT and DVID
VTT adjustments are made over the default value which is different for different platforms. That is why I refer to VTT in +0.xV adjustments. DVID is a very cool feature, but my guide is writen to no use it, please disable it! If you want to explore DVID possibilities, please start a thread to discuss it (if I don't chime in, PM me and give me a link to your thread so I can help out)

OCing can get very complex, so I thried to make this guide as green friendly as possible, while still empowerin users with the basic knowledge to understand what they are doing. It's a lot to swallow in one sitting, so take your time, and don't rush Best of luck, and don't hesitate to call on the users here for help

Thanks for getting the update published while I've been out of town Hokie

A huge shout-out to Senior Member "Brolloks" for his invaluable input on this update....I couldn't have done it without you man!
freeagent's Avatar
Thanks for the write up! This noob finally cracked 4.2 on my ancient C0 last nite, and it didnt bluescreen with large ffts like it always does! It has been my first intel chip where it actually challenged me to get a ghz over stock, usually you are pratically guarenteed it
ewoogy's Avatar
Thanks, helped a lot! This is my first time to ever try to overclock anything and i got my i7 920 to 4.0ghz with no problems at all. Thanks for helping the new guys!!!
Lvcoyote's Avatar
I'll concur with the weak IMC issue on these 32nm CPU's. I was going nuts trying to overclock this i5 661 past 4.0 GHz, until I dropped the ratio to 2:8, off and running now!!
DHEnthusiast's Avatar
Love reading OC guides, nice one!

Learning all I can
Brolloks's Avatar
You are most welcome my friend, glad I could add some value to your already excellent guide
Aynjell's Avatar

Quad core i5 CPUs (Lynnfield) are identical to the low end i7 CPUs, the only exception being the lack of Intel Hyper-Threading Technology. All i5 CPUs work only in LGA1156 based motherboards.

I5 750 being the only quad core out right now, you can add to that blanket statement "and vt-d, which allows virtual machines direct access to the hardware."

See the following:

It's basically the stuff required for using real 3D hardware in VM's. I say give it 2 more years and somebody will come up with some type of shell operating system that lats us run Linux and Windows in parallel. A super lightweight and flexible hyper-visor...
Interesting, you are correct sir....thanks I missed that one
hokiealumnus's Avatar
Now that you mention it, it's also missing "Intel Trusted Execution Technology (Intel TXT)", for what that's worth (nothing for most).
Hokie...would you mind making those corrections please?
hokiealumnus's Avatar
With appropriate linkage of course.
Aynjell's Avatar
TXT I'd argue is pointless. I've never had issues without. I know I wouldn't mind an i7 860 so I could get HT and the vt-d for future use. I'm praying for the day when we can run comsumer OS's on a hypervisor. I'd love to be able to utilize all my hardware natively and be able to swap between os's at will. A man can dream, right?
Brolloks's Avatar
Now that would be great...then again that is what I do 99% of the time in any event...knock on wood I have only had a few bad OS adoptions, most of the time I have a seperate dedicated OS drive for my X58, P55, P45 and X38/X48 boards, it does minimize issues.
DreadCthulhu's Avatar
The guide mentions that sometimes the machine might not post at all and then you'll pretty much have to reset the bios. A couple of related question:

- What is usually the cause for the inability of the computer to post? Low VCore or VTT? It'd be good to know in case you made a tweak and all of a sudden the box won't boot and you have no idea what can be improved about the previous set of settings.

- What do you do in case there's no CMOS reset button? Pull the battery out?

- Sometimes a certain set of settings works fine and resets fine, and is perfectly stable throughout tests, but then it might not post the next time you turn on the machine. Why?
LittleJay's Avatar
thanks for the guide it was a great help
If anyones interested ive worked out an equation to find out what your graphics clock should be set to to keep it from overclocking with your base clock.

a=Overclocked Base Clock
b=Default Base Clock
c=Default Graphics Clock
x=New Graphics Clock


for example say you have an i3 with its gfx clock at 733, your default bClock is 133 and its overclocked to 210

a/b = 210/133 = 1.5789...
c/1.5789... = 733/1.5789 = 464

So you would set you gfxClock to 464

Hope thats useful for someone
Brolloks's Avatar
Very good questions See above
DreadCthulhu's Avatar
Thanks for the responses. About the last point, I'm getting this strange "won't post despite good stability" issue right now on my box. It was working fine before I started OCing, but once I started then it would occasionally either:

- start to boot, but then audibly restart before the post screen. Sometimes 1-3 times, then eventually it would post and work fine afterwards.

- not post at all, which is what I ran into.

The reason why I don't think the RAM is the issue is because this no-post issue was never there when the system was at stock values, so I'm trying to determine what exactly was fubarred.
Brolloks's Avatar
What CPU , RAM and board are you using? When I say RAM is not compatible it is really at OC state, at stock pretty much everything should run fine 99% of the time.
DreadCthulhu's Avatar
I'm using:

2 x G.SKILL 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800)

Intel Core i5-750 Lynnfield 2.66GHz

GIGABYTE GA-P55M-UD2 LGA 1156 Intel P55 Micro ATX Intel Motherboard

What's ironic is that I picked those sticks specifically because they were supposedly compatible with that board.
Brolloks's Avatar
What was your OC when you started getting issues and what voltages were you applying?
Not that the UD2 is a bad board but it has limitations to OC.
DreadCthulhu's Avatar
Actually I lied. I just reset the settings through the jumper and it still takes 2-3 attempts to boot.. That's weird. Shouldn't be the lack of power either, it's a 750W PSU.
wickedout's Avatar
Very nicely written. Great read and good understanding for many of us. Thanks again.
Brolloks's Avatar
I would venture to say your board is FUBAR, RMA it or return for exchange.
psionic98's Avatar
1 - on initial post---bad factory setting.. resetting cmos helps usually or its a dead board
2 - yes pull battery for 30seconds and replace
3 - not sure, can post this in another thread on its own
jamsde's Avatar
Wow what a very well written and informative guide, thank you so much for posting it! I just finished building an i920 system for gaming and will be using your guide to tune the overclocking. Thanks again! I'll post my results

Thanks for the positive comments guys....I'm glad we could help

Please post your specific system related questions in a new thread. This thread should be for comments or questions about the guide only, thanks
dominick32's Avatar
MIAH, just took a gander at this on the homepage. Excellent review bro!

urasofty's Avatar
Hello ive been following this guide and i just have a question regarding vcore.
Im using p55m-ud2 mobo + i3 btw. When im trying to tweak my vcore how do i increase it in increments of 0.025V? in the bios the only available options are 0.5V+, 0.550V+, etc. am i missing something here?
dominick32's Avatar
Dont worry my friend. This is just a general guideline more along the lines of "raise vcore how you feel comfortable doing it". If your motherboard only allows certain intervals than use the smallest interval offered.

However, I think you may be wrong with your numbers. A bump of .50 is not possibly the smallest option on a mobo seeing that normal VID is between .98 and 1.3625 on Intel processors, so bumping up vcore .5 would essentially burn out your chip with too much heat and volts in one simple bump. lol So, I am assuming you mean .055v? Please make this correction before we proceed.

urasofty's Avatar
Sorry, I'm an idiot >_<. While looking at vcore in bios i assumed that every bump is added to the listedl cpu voltage (i.e. 1.103V + 0.50). The minimum number given was 0.50 which obviously means changing the voltage to 0.50 not actually bumping it by 0.50. Stupid mistake ! =[
baditude_df's Avatar
What a fantastic Guide! It's really well laid out and an easy read.
Thank you MIAH and all who contributed!

But what's missing from this picture?
:looks down at poor lonely 950:
Thanks Pat...

I left out the i5 950 just for you
urasofty's Avatar
After a couple weeks of using stock cpu speed i decided to try my hand at ocing but have run into some problems. Here is the build - core i3, p55m-ud2, arctic cooler f7 rev 2, 4gb kingston 1333 ddr3- 1.50V stock
Right now my oc is sitting at
3.65 ghz
multiplier x22
bclock 166
vcore on cpu-z @ max load 1.072V
@ bios 1.09v
vtt - 1.20V or 1.10v (stock
ram volts - 1.50V (should this ever be increased)

I've pretty much followed your guide (ram timings, lowest multiplier,etc). I've found leaving the vtt stock while increasing vcore slightly to be just as successful as increasing the vtt and vcore.

Anyways in an attempt to oc a little higher I've experimented by slowly increasing vcore, and bclock to 169,170,175 and it would boot then continue to restart eventually loading default settings if i do not go into the bios. The highest vcore i had was 1.25v @ 172. I'm not sure what the problem is, what are some numbers i should be testing out?
i have not yet increased the ram voltage because i am not even sure if this should even be increased in the first place.
1st question - are you using the iGPU? If so, did you read this section?
2nd question - what was the maximum stable bclock freq you found in step #1?
urasofty's Avatar
Sorry i forgot to mention i have the hd 5750.

I'm not at home so i can't test the maximum stable bclock right now, but the highest i could get so far (with memory timings set manually and mem volt set to auto, mem at 2:6) was 185 block (what im aiming for) x 19 multi @ 1.08 vcore and 1.21 vtt (would you recommend leaving vtt at stock 1.10?) which posted at 3.51ghz. Everything else was set to auto. I tried running 185 x 21 loaded windows then got the BSOD. I ran prime95 before I left, and it was stable for 5 minutes @ 185 x 19. It's still running so ill check the stability when i get home.

I also ran prime95 overnight with the settings in my previous post and got an error after one hour so that one wasnt stable -.-.

I forgot to mention that when i set the mem timings in the BIOS 9-9-9-24, cpu-z reads it was 7-9-9-24. Is this normal?

Im trying to hit 3.9-4 ghz using the lowest vcore. If possible not exceeding 1.25 vcore.
OK, my first thought was this was iGPU related, and they almost always start giving problems around the same bclock range, but getting that out of the way, we're on to bclock and CPU OCing....steps #1 & #2 in the guide.

So when you tested for high bclock, you were using 185MHz with 1.21V VTT correct? You also had the CPU multi at x19??? Try for max bclock again with CPU multi set to x12 or so. If your goal is for 185MHz bclock, then got 190MHz stable for at least 1 hour. You may need more VTT...1.21V is not a lot, running 1.35V is perfectly safe for an air cooled rig

Then go back to 160MHz and bump up the multi to you desired setting, and the CPU voltage to 1.25V, then 5MHz at a time test as described in the guide and see if you can get it back up to 185MHz bclock. You may not get there though with so little voltage. Most CPUs need at least 1.3-1.35V to get to 4GHz, but you'll never know until you try.

If you need more help, please start a new thread so this one can remain on the topic of the guide Thanks, keep us posted
urasofty's Avatar
I'd like to formally thank you for the help . Was able to get 3.85ghz stable at low volts following your steps. Great guide !!! Thanks again.
13rian's Avatar
Maybe this is a silly question, but is 1.35V really safe for an i5-750? I ran across this Anandtech thread stating the Lynnfield max is 1.21v VTT, while the older Bloomsfield is 1.35v VTT. I'm completely new to overclocking so I just want to make sure I'm as informed as possible and don't make any major mistakes. Thanks!

FYI, I plan to use your guide MIAHALLEN. It's the best one I've seen and I already have it printed out.
Brutal-Force's Avatar
The Vtt suggested by Intel is way off. Additionally, in order to run a larger ammount of RAM, you will need to up your Vtt. Call your RAM manufactuerer and they should clear this up for you. I run my i7 860 at 1.41V Vtt. If I am overclocking at 4GHz anything less than 1.25V will BSOD on me and anything less than 1.2 won't even boot.
Yup...Brutal is correct...1.35V is perfectly safe...I know many users who run more. I run my Bloomfield at 1.5V 24/7
Oc1Kenube's Avatar
Excellent guide, sure to come in handy as and if i deem it necessary to go over 3.8ghz
diaz's Avatar
Thanks for guide!
sizmike's Avatar
Cool article ! I'm going to apply this.... I've been reading articles for about 40 hours or more, but have to say there is a shortage of up to date beginner guides for noobs like me, so i'm gratefull for the info. Read it several times while surfing web for info.


i5 661 (stock)
4GB PC3-10666 1333MHz
Asus P7H55-M Pro
Radeon 5770 1GB GDDR5
Dual Layer DVD Burner
Hard Drive: 500GB
Cooler Master eXtremePower Plus 600w
Case: Cooler Master Centurion 590
Windows 7 Home Premium 64bit

My goals:

I'd like 3.7-3.9Ghz Nominal with room for Intels' Turbo Boost taking me to 4Mhz. According to my research my target should be about a 150 -155 MHz bclk and near stock volt's.

I bought this system and installed BFBC2 after playing BF2 for years, it does ok, but I have to turn down AA, AF HBOA = off to get 50 fps. If I want 60fps I have to drop res from 1900

1a) IYOP, what's my bottleneck ? CPU or GPU ? I plan to O.C both if I have to.

1) Does the iGPU chipset switch off entirely when you add a graphics card into the mix ? Do I still have to tweak the BIOS settings for the iGPU as instructed in GUIDE or can I forget about them for the OC?

2) OC'ing parameters aside, resetting the BIOS to default settings is scary to me, I've never done it before, never had a reason to. Wasn't it config'd by the builder in the shop for my specific system ? Is there a chance that other important settings besides the ones used for OC' be affectied negatively ?

3) Please confirm... Disable Turbo-Boost and Speed-Step ? Disable before starting to OC or leave enabled ?

Thanks to all who respond !
to OCF
If you have any more questions, please start a new thread so it will get more visibility from the whole community
dkizzy's Avatar
nice guide mia it was informative and will help me with pushing my new i7 system and seeing its limits.
Sorry, I don't have time for a proper reply now, but I will address your post when I return from a quick trip in a couple days (walking out the door in a few minutes)....great suggestions here
Nhut Pham's Avatar
I got one question for you miahallen, when you say it's dangerous to have the VTT and VDIMM more than 0.5V apart, does that mean you want to minimize this difference as much as possible?

I am working on an overclock that is stable with VTT at 1.17V. I am currently running my ram at 1.66V. I don't know what is better, running my VTT lower or perhaps making my VTT closer to my ram voltage. I assume you wrote that in to mean for the case where people are putting lots of voltage on their ram, but I'm wondering what's the best setting for my particular chip.
nzaneb's Avatar
If you're stable, then there is no need to raise your VTT as you're within the cuttoff. Low VTT will definitely help lower your core temps. I wouldn't try to go any lower though
Nhut Pham's Avatar
Yeah, I'm actually more stable at 1.17 VTT than at 1.35 VTT, I have no idea why, maybe I need to do more testing. I almost wanted to go lower, but haven't in fear that I might damage my CPU. What else is strange is that my ram is more stable at higher voltage than before, like I said I probably need to do more testing. Could also be because I got a new motherboard.

I got a replacement cpu from Intel, and I've been messing with it. It has a very strange batch number, L003B806, and has a very recent pack date 4/27/10. Requires a lot more voltage than my last chip to be stable for LinX, but runs cooler than my last one by more than a few degrees, even at higher voltage. I'll test out some more when I get my Venomous X in the mail.
Bruce, thanks again for your comments, please see my answers to your questions below

Again, thank you Bruce....and to OCForums
Bruce....a lot of good questions and suggestions. If you have more, screenshots would be helpful, and if you create a new thread in this Intel CPU's section, more people will check it and be able to assist. I'm a little rough around the edges with Asus boards, so the additional community support would probably be benneficial, thanks
madyville's Avatar
hi ... excellent article , i need help in my case as i have Intel motherboard and there is not much scope of over-clocking as i have learned ...pl assist as to what can i do to maximize performance.

I am also facing a weird problem, my computer hangs and slows badly while multitasking having a quad core processor . I have checking my CPU usage while running processes which is normal . Tried on XP and Windows 7 and it was a nogo ..please help someone !! . Here are my specs.
hokiealumnus's Avatar
Hello madyville, and welcome to OCF!

To best assist you, I'd recommend starting your own thread rather than tacking this on to the end of this one. It seems you have issues that need to be addressed before you begin attempting to overclock.

I'd recommend starting in the Microsoft Operating Systems area. If it's determined to be hardware instead of software, it can be moved to the appropriate section. Be sure to list the applications and background tasks you have running when you experience the hangs. Best of luck!
DocNick's Avatar
Nice guide man! Saves me for a lot of time!
to OCForums DocNick, glad the guide was helpful for you
gosa's Avatar
Found this forum searching google for some hints on overclocking my i7 860 and like some of the other posters I just had to register to post my appreciation.

Only problem I have now is to make a good chunk of time available to try this out without the gf complaining to much...
Ace.'s Avatar
good Guide!
Here my i5-661 @4,7Ghz LinX and Prime stable

Hey guys.... to OCForums to the both of you!

Nice....thanks for stopping by Stick around a bit

Whoa ....nice OC
verysoon's Avatar
never had i register in any OC forum just to say thanks.

where i come from, it's very hot, like always in the 30c ~ 34c range. 100% load on my stock intel cooler can easily hit 90c.

even thou, u made me dauntless in my impending attempt to OC, at least to 4ghz.

Thanks mate....glad it was helpful
gosa's Avatar
I sure will...

Been doing some initial testing and I've managed to get my i7 860 up to 3,8GHz (BLCK190*20) so far... the voltages I've used are 1.3V for VCore and 1.3V for VTT - With that I'm stable for a full night, and temps keep between 75-79C running Prime95 which means I can do most of my "stuff" at temperatures around 70C.

I do have serious problems taking the step up to 4GHz though, because right now I just don't have sufficient cooling for that... Need some better fans in my box first (but that's a question for the "cooling" section.

Anyway - Thanks again for the guide, now I'm looking forward to the next step!
Joe12's Avatar
Hi, this is my first time overclocking. Thanks MIAHALLEN, for the amazing guide, it cleared up alot. I am overclocking an i7-930, and I have a question about the QPI clock ratio. You mentioned that it is a function of the bclock, so should I just keep the QPI clock ratio at 'auto' since it will be increased as I increase my bclock, or should I change it to something else? (I can chose between x36, x44, x48, and slow mode). If i do keep it at auto, when (if ever) would need to change it?
Hey Joe, to OCForums

If you leave the QPI ratio on "auto", most motherboards will set it to x36 when you OC....and that would be fine. If you'd like to set it manually, do so at x36. And no, there would never be a need to change that unless you want to push the bclock to the limit for benching (not for everyday use), in that case "slow mode" sometimes helps a bit
virang.dalal's Avatar
I am planing for a complete update. I am getting a i7 930. Which motherboard is better?

ASUS P6X58D-E -- $239(apprx)

Gigabyte GA X58A-UD3R -- $209(apprx)
wkchan1979's Avatar
thx MIAHALLEN for great info especially newbie like me!!
nod question here, if i would like to fix my CPU clock to 3.9Ghz but i doubt which option i should increase, either BCLOCK or CPU Multiple? there are few combination i can play around this two option to get 3.9Ghz but what is your suggestion? Increase BClock or CPU Multiple?
thx again!!
EarthDog's Avatar
Unless you have an unlocked multiplier chip, you cant move your multi up outside of the turbo function (which on most boards can be permanent).

With that said, IMHO, thats the game, a nice solid bclck will improve performance a bit more than only a raised multi.
wkchan1979's Avatar
thx! i tried play around and found Temp increase more if increase BClock compare to CPU multiple... too bad. btw another nod question, will SPD number lower will be better? i try change from Auto to 6.
thx a lot!!
EarthDog's Avatar
You cant change SPD number...thats just a setting for a specific speed. You would need to know your memory's default timings/voltage (the SPD you were talking about!). I would set those 4 main timings manually as well as the voltage.

You can change the memory latency speed though (which was what you were talking about with just the wrong terminology). I doubt you will be able to go to 6.
wkchan1979's Avatar
you are right sir. it just died when try to restart. i have to reset the BIOS so should i put into Auto mode? as i saw memory frequency at bios shown more than 1333(default) = around 17++ when i set to auto mode and it can reduce by put the SPD to 6... would should i do then. thx again!!
EarthDog's Avatar
No set it manually as mentioned above.

Dont bother with CAS6 really. If 7 is stock, run it there.
wkchan1979's Avatar
thx!! let me have a try and review again the tutorial. i must be miss out something that i yet understand... Thx!!!
ufc's Avatar
So I am using a stock intel cooler with an i7 920 so you say in the first step to increase the CPU VTT to +0.2V and then perform a few tests if the first test fails to increase the CPU VTT by a small increment(what exactly is considered a small increment 0.05?) but its already at the maximum safe voltage. So do I just adjust the bclock frequency and leave the CPU VTT Voltage alone after setting to +0.2V in step one? Sorry just a bit confused here. Thanks
That is correct Since you're using the stock cooler, my reccommendation for starting voltage, is also the recommended max, if you feel more would be benneficial, I would suggest getting a better cooler first

Good luck, and keep us posted. Feel free to start a new thread so more people will look at your questions
Philippe's Avatar
Hello, I'm new here and it is my first overclock attempt since celeron days (I think i had a celeron 500 running @ 800 mhz for years... not sure if I remember correctly). Thanks for your guide. It was much more helpfull than every other one I saw.

So I recently bought an asrock p55 extreme with i7 860 and a noctua cooler and I'm aiming for 3.8 Ghz and trying to keep the voltages as low as possible... But I wanted to see where my rig's limit was first so I got it to 4.1 Ghz stable, albeit hot thanks to your guide.

So here's my question: while determining the max bclock I realised that I can get it stable enough @200mhz to sustain 15 minutes of Prime95 with VTT voltage slightly above stock setting (1.23). But as soon as I hit 201Mhz (or more) the mobo refuses to POST and no amount of VTT voltage increase helps and I tried to raise it up to 1.5v (stock setting 1.21v ) + 0.3v like you said?? Is it normal or did I miss something ?
(maybe a cryptic bios safeguard option enabled? but then why allow me to break the 200 Mhz barrier in the first place?)

I am now running @ 182x21 with 1.225 vcore and all the other voltages at stock levels... and it looks stable though I'm still in the early stages of stress testing. Load temperatures do not go over low 70's. Thanks again for the guide. It's the best out there.
redduc900's Avatar
Try raising the PCH Voltage from the default of 1.066V to ~1.15-1.20V for BCLKs >200, this w/ VTT Offset Voltage at ~1.25-1.35V
beuch's Avatar
I just used the Miahallen guide to overclock my i3 530 with an asus p7h55-m pro motherboard and kingston valueram. The guide was very informative and covered all the pertinent issues very well. I'm currently oced to 3.5 and I'm going to go up to 3.8 or higher once I replace the stock cooler.

My one complaint is that the guide could have been organized better. It seems like it is always leaping back and forth between instructions and explanations. I found this guide a bit more clear and concise and it offers virtually the same advice: http://lifehacker.com/5580998/a-begi...ntel-processor

I would recommend reading both guides. I believe the Miahallen guide provides more information but, for me, the lifehacker guide makes the actual procedure you are going to execute a bit clearer.
Philippe's Avatar
Thanks Redduc. I just tried that and still no POST. I just had to clear the CMOS again.
THanks for the feedback!
Interesting bclock wall you're running into...try raising the PCIe link speed to 105MHz and see if that changes anything

Thanks for the feedback, and the link. I'dd consider the info in the other guide when it's time to do the next update.
Philippe's Avatar
Thanks for the answer... I tried to raise pcie frequency but it still won't POST.
goldenlight's Avatar
This is a fantasic tutorial on overclocking.. Can't wait to try this later with my new hyper 212 plus cpu cooler.

I havn't overcloced a cpu since the old Athlon days.
zez's Avatar
Yes, yes. This tutorial was a great help. I've been out of the overclocking game for a while, and this tutorial got me up to speed.

Now my i7-930 is chugging along at a nice 4GHz
Aynjell's Avatar
Mia just wanna say you rock, bro. I got friends who are using this guide on their first Intel chip. You're making their life very easy!
Thanks for the feedback guys, I'm glad it's helpful
minority01's Avatar
i tryed following this guide but when ever i make the first changes to the voltage and cpu and memory Multiplier it wont boot
im using an i5-661 on a GA-P55-UD3 motherboard
reseting the bios works but it fails when ever i change it
please help
minority01's Avatar
wait dont worry, i fixed it, updated the BOIS
also, do i need to worry bout the iGPU if my motherboard doesnt support it?
Sorry, I missed your first question....glad you figured it out
No, if you've got a P55 mobo, you don't need to worry about the iGPU, it's automatically disabled
dg170775's Avatar
Hey Miahallen, great article. It sounds even more appropriate to someone like me who just started overclocking, without a lot of knowledge, on the terms, etc.
Today, I'm sitting @ a stable 4Ghz system, but, I am planning to again start from basics, based on your article.
I have a i3 530 on an ASUS P7H55-M board, with 4GB Corsair XMS3 1600Mhz RAM. I am relying on the iGPU as I'n not a keen gamer, and budget's constrained

One question: Was 26th Feb the last update to your article, as I did see a lot of further questions / answers? And there was an update coming out...

I will let you know how the OC goes.
Yes, I started working on Rev 3.0 today....should be a week or two

Start a thread and let us know how it goes with that i3...great chip and most are good for 4.4GHz or more
dg170775's Avatar
Cool... Looking forward to rev 3.0
For my current OC exercise, i've taken a print of your article with all comments / questions / answers, as there's plenty of information there, especially for my H55 board (ASUS P7H55-M)
Will start a thread soon .... and update progress ...
dg170775's Avatar
Hey Miah,
Sorry, have been a bit busy off late, but I can definately say that the Rev 3.0is a much refined upadte, as I used it to overclock my i3 530, right upto 4.24Ghz. I still have the potential to go higher, but, I've just taken a break.
But, this is for anyone starting fresh, like me, this guide is a dream ..
Continue the great work, Miah !!!
virupaksh's Avatar
Hi Dude,

I have a PC with i5 650 , gigabyte HPM-USB3 model nd 4 GB Transend DDr-3 1333. Now Will overclocking work properly on my pc and how can I attain the maximum frequency of my RAM. Im very new to all these overclocking concepts. Please help.
dg170775's Avatar
Follow Miah's guide to overclocking, you can't go wrong there .
I've used his guide and it clears several things easily ..
Infact, in my first attempt, I was able to get to 3.6Ghz
And today, I'm at 4.22Ghz, all because of the guide..
Let us know how it goes .. and if you get stuck, create a thread here, and you'll get solutions ..
Happy overclocking
Word's Avatar
First poster here...

I'm new to overclocking. I've followed the guide best I could. How do these settings look?
i5-760 w/ MSI P55 GD65 board.
1.85x21 (3885 MHz)
CPU voltage - 1.345
CPU VTT - 1.266
DRAM Voltage - 1.645

Those look like a good start, the CPU voltage seems a tad high....what cooling are you using?

Were you using the new guide (linked in my sig)?
Word's Avatar
It was a different 3 step guide to overclocking. Yours was easier to understand. Here is where I ended up with your guide...

I left all the power savings features enabled.
Low clock: 183x9 with ~19w power consumption
high clock: 183x22 with ~126w power consumption -- Just under 4GHz
CPU Voltage: Auto (not sure if I should leave this or not) I don't recall what the bios has, but CPU-Z states 1.408 V for the Core Voltage.
QPI/VTT: 1.303

I'm really liking this so far! I was able to turn the CPU fan and all system fans to 50% and only gained 3 (84 max) degrees with IntelBurn.
Word....I wrote a guide at the beginning of the year, and then I updated it earlier this month....which one are you using? This is the one you should be using:

Word's Avatar
This is the one I used the first time link and was somewhat confused. My confision was with the different terminology used between board manufactures.
Yesterday I used your guide for the lynnfield link and it was much easier to follow. The bois comparison chart really helped out too!

Thank you for taking the time and writing this up!
Arnolddk's Avatar
First of all im a complete newbie when it comes to OCing. However this guide is very newbie friendly (Thx alot), and got me eager trying to OC my Cpu.

My spec is:
I920 2,67ghz(Currently at 3,6 ghz)
Cooler: Noctua nh-d14

Im doing pretty fine raising the Bclock x<180, and it works fine using either low multiplier 12 or high multiplier at 20.

Whenever I raise Bclock to 180 or higher the system wont boot and im forced to clear the bios by manually switching jumpers on my m-board.

At first I thought it was because I forgot to raise the voltage as well. Although ive tried voltages at 1,3375 and higher(Default was 1,15) the system still would not boot. I even tried raising VTT accordingly matching the vcore but without any luck. Actually had VTT at 1,50 at some point just to see if I could get some sort of reaction, but afterwards stopped trying since my impatience might let me turn up the voltages even higher!

Is there something else than raising voltages that would make my system unable to boot at 180+ bclock. Seems to me most people with the i920 have no problem at all going alot higher.

I would appriciate any hints

edit: Reading above post, I noticed that theres a newer version of your guide. Imma go through that one, since there most likely is something I missed out on
Tyreally's Avatar
I already have a nice stable i7-930 oc of 3.8, but I wanted to go higher, so I thought I would try your method of oc. But, I have read through it and have some questions:

Current 3.8:
multi= 19
blck= 200
qpi vtt= 1.2
ioh= 1.14

Basically, you start by finding the your desired bclk with the best qpi vtt and ioh core. Since I already have my desired bclk and the corresponding qpi vtt/ioh, is there a point in re-doing this step? I.e. my desired blck is 200 - right now my blck is 200, qpi vtt 1.2, and ioh 1.14.

** My bedhead is telling me that if I redid this step I should not find qpi vtt going into the 1.3 range - but:

The last steps require multi and core to be adjusted (not qpi) - which seems fine, but, based on seeing other people bios setups for 4.0-4.2 oc, I will required more qpi vtt to get it stable.

** well now my bedhead is telling me that the first step should indeed show a larger qpi vtt, but then the logistics of this whole situation don't seem right to my bedhead...


Don't worry about what other people need....all chips are different, and it sounds like yours is very good

And to answer your question....you are correct. If you're happy with your bclock/memory settings, you can jump straight to step three and go from there. Just be sure you really are satisfied with the stability of bclock/uncore/memory first
Arnolddk's Avatar
Hi again. Ive read your updated guide through and realized I had forgotten to update my bios.

Ive updated my bios but still no luck. Current working BIOS setup is:

Genie Bios Setup:
Exit setup shut down= mode 2
O.C Fail Retry Counter = enabled
O.C Fail CMOS Reload = Bank 1

PPM Function = enabled
Turbo Mode Function = Enabled
Cpu multiplier = 21

Bclk/uclk/qpi controller settings
QPI Control Settings = Enabled
QPI Link Fast Mode = Enabled
QPI Frequency = Enabled
CPU Base Clock = 175mhz
Boot up CPU Base clock= atuo
PCIE clock =100 mhz
DRAM frequency =Bclk *06 1050mhz
Uncore frequency =Bcllk*12 2100mhz
CPU speed spectrum = Disabled
PCIE Spectrum = Disabled

CPU Feature
All disabled except
Intel H1 Technology = enabled
Active Processor Cores = all

Voltage Settings
O.C. Shut Down Free = Enable
CPU Vid Control =1.3375V(Could be lower but wanted to test cooler)
Power Savings =advance
Super VID =Off
Vcore auto PSI = Disabled
OCP = 140A
DRAM Bus Voltage= 1.560V
DRAM PWW Switch Frequency = Nominal Frequency
DRAM PWW Phase Control = 2 Phase Operation
CPU VTT Special add = Atuo
CPU VTT Voltage = 1,34V
VTT PWW Switch Frequency= Nominal Frequency
VTT PWW Phase Control = 2 Phase Operation
CPU PLL Voltage =1,80V
IOH/ICH 1.1 Voltage = 1,11V
IOH Analog Voltage = 1,10V
ICH 1.5 voltage =1,5V
ICH 1.05 voltage = 1.05v

I left the Dram timings on auto.

Computer specs are:
Operating System
MS Windows 7 Ultimate 64-bit
Intel Core i7 920 @ 2.67GHz
Bloomfield 45nm Technology
12.0GB Triple-Channel DDR3 @ 525MHz (6-6-6-15)
DFI Inc. DFI LP DK X58 (LGA 1366)

ATI Radeon HD 4870 X2 (ATI)

Noctua NH-D14 CPU Kler


Since increasing cpu voltage doesnt help boot up at 180+ blck, I figured something else might be wrong. I just a little worried I might turn something up to high just to get a reaction, since now all I can do is a hard reset of the Bios everytime I raise Blck.
You should copy this information into a new thread so more people will look at it

First thing I noticed is that your DRAM voltage is too low. Set it to 1.65V
Also, if you're still working on bclock frequesncy, your CPU ratio should be low to isolate the bclock like the guide says.
Arnolddk's Avatar
Ya my bad. I can actually use whatever multiplier and will boot up at 175 bclk. Soon as I raise it to 180 it will fail even if the multiplier is isolated. (tested 12, 14, 16).

Ill make a topic as you suggested once ive changed the DRAM voltage. Thanks for the input however, ill try the changes once im home from work.
xoke's Avatar
Thank you MIA! I will be following this guide tonight for sure.
Make sure you use the updated guide (linked in my sig) it's much better
HowsMyShooting's Avatar
Alright thanks for pointing that out it hink i will read up on that now the 3 step guide and go off that
gero1369's Avatar
Wonderful guide. Worked very well for me.

One suggestion. I'd start the third step with the vcore at 1.25 or even 1.2, then start raising the bclk...

I did that and am getting an OC at <1.275 v with great results (3.885 GHz, i7 930, <90 C).

Just a suggestion. I've seen many others with similar OCs and voltages to mine.
Thanks for the comment gero....I've completely re-written the guide (the new version is linked in my sig) and it starts off step 3 with 1.2V
viking80's Avatar
Great and very useful guide. Knowledgeable author. First time try on a i5, and wonderful result!
The i5-650 is pretty much unlimited by multiplier if you use 1600 or faster memory:
- gigabyte H55-USB3
- 2x4GB DDR3-1600 @800.1MHz 2:8 divider
- Thermaltake Silent 1156 CPU cooler: 35 C idle, 70 C full load.
- with all voltages unmodified except Vtt + 0.15V
- bus speed 200MHz multiplier x23 = 4.6GHz!

Fantastic performance and built in decent graphics.

Did one unusual thing. I cut away for full holes for the fans instead of hundreds of small holes, and installed a fan guard that came with the fan. This increases the airflow 10x.
viking80's Avatar
[QUOTE=viking80;6704794]The i5-650 is pretty much unlimited by multiplier if you use 1600 or faster memory:
- gigabyte H55-USB3
- 2x4GB DDR3-1600 @800.1MHz 2:8 divider
- Thermaltake Silent 1156 CPU cooler: 35 C idle, 70 C full load.
- with all voltages except Vtt + 0.15V
- bus speed 200MHz multiplier x23 = 4.6GHz!
BTW, this is a backed down setting. Hihest stable was 208=2.8GHz!. Got unstable at 210MHz. Backed down to 200x23 for extra stability headroom.
J2Fresh25's Avatar
awesome read...I have decided after much deliberation and the urgent need of a new comp as my MOBO appears to be failing( to go with an i3 550 setup, going for 4ghz stable) anyway Im broke and the barebones from Tiger Direct seems to be a good kit to start with)
Convicted1's Avatar
Any chance somebody might want to take a stab at updating this for SB?

Or maybe just post the glaring differences...
MattNo5ss's Avatar
I believe Miah has a SB version over at TechREACTION.
Convicted1's Avatar
I found that... I thought it looked similar, but didn't know they were written by the same person.

I was looking for MORE to read. LOL

I'll just stick to the guide posted at TR then.
hokiealumnus's Avatar
Heh, I can do it pretty quickly:

1. Raise Multi
2. Test
3. If pass - repeat #s 1 & 2, else to go to #4. If blinking cursor, go to #8
4. Raise Vcore
5. Test
6. If pass and within thermal limit - repeat #s 1 & 2, else to go to #4. If not within thermal limit, go to #5.
7. Thermal limit reached, stop.
8. Brick wall.

Seriously though, we can help if you need it. Are you stuck somewhere? Or you could start a thread.
MattNo5ss's Avatar
Yep, same guy.

SB is pretty simple. For 24/7 clocks, you just have to mess with the CPU multiplier and vcore really.
Janus67's Avatar
Important to note that this guide is for the first generation of i-series of processors, not the 2nd gen (sandy bridge) ones.
I did do an updated version for Sandy Bridge here
micjmac's Avatar
I'm confused. You first found out the highest stable bclk. Then when you focus on the memory you are pushing the bclk past its highest stable frequency by 2 MHz increments. Please explain.
Janus67's Avatar
IIRC you are to drop your Bclk down to where it was at stock then increase in 2mhz increments, you don't start from the highest stable bclk levels.
micjmac's Avatar
So the whole point of the bclk phase and the memory phase are to find your optimal VTT and DRAM voltages?

Because ultimately in the end, you are dropping the bclk all the way down and upping the CPU multiplier before you start tweaking the Vcore in unison with the bclk.
Janus67's Avatar
That is correct, as you need to find the voltages for the QPI/VTT, the DRAM, and then for the Vcore for the CPU, but it will also give you a point where you know that you will most likely max out so that you don't start adding more and more and trying to determine if what you are being limited by.
micjmac's Avatar
So then it's possible that your memory limits your overclock? Let's say my max bclk is 200. Then I change it to 133 to test the memory by 2 MHz increments. What if I can't get the bclk back up to 200 while increasing the DRAM voltage? By that rationale my VTT would be higher than necessary.
Janus67's Avatar
correct, you will want to find out what your VTT needs to be at the level that you reach at for your DRAM if it is indeed the limiting factor.
There is a much greater bennefit from overclocking your CPU compared to your memory. If you cannot reach your bclock goal due to your memories limitations, I would suggest running the memory slower in order to enable you to push the bclock/CPU up higher

For instance, if you had DDR3-1866 memory, and you were trying to get the memory to run at DDR3-2000 (corrosponding to a bclock goal of 200MHz), then I would drop the multiplier down to have the memory run at DDR3-1600 instead. To compensate, you could attempt to tighten up the memory timings....which is often easier to do then pushing up the speed.

My guide does cover this concept
micjmac's Avatar
I do not have an IOH or ICH core voltage.

I do have 7 voltages that are not listed in the article though:

1. PCH Core
3. DRAM Termination
4. Ch-A Data VRef
5. Ch-A Address VRef
6. Ch-B Data VRef
7. Ch-B Address VRef

Should any of these be considered?
None of those are important except for possibly #3.
Do you have a voltage listed in the BIOS called "DRAM voltage"?
If so, then #3 is not important...if you do, then treat #3 as the "DRAM voltage"
sarp's Avatar
Ive i3 530 @2.93

Ive managed to get it to 4.00GHz with 182 BClk by changing QPI, Graphics and RAM Frequencies accodringly. Sometimes my screen just freezes with a solid color and I have to restart it in order to get to Windows again. Anyway, I want to boost Intel Graphics HD 3000 performance, it's default clock is 733MHz, since Ive changed BClk to 182, to be on the safe side it is 500MHz. I wonder, how much should I increase graphics core voltage in order to get to 900Mhz with 182 BClk?
daz2711e's Avatar
i have i7 930 with p6t motherboard and there is no memory multiplier option.what should i do with my ram??
redduc900's Avatar
Asus integrates the DRAM multiplier / BCLK : DRAM ratio into the DRAM Frequency option. So at a given BCLK the BIOS automatically configures and offers DRAM frequency options based on the available multipliers, for example x6, x8, x10, etc.
Daniel089's Avatar
I want to ask something: Can I follow this tutorial when I want to overclock my Intel i5 760 CPU on my P7H55 motherboard? Is there a notable difference between overclocking in a P55 and H55 motherboard? Thanks in advance!
Dartmaul's Avatar
Really enjoyed this guide, but still have few questions.

1) What about CPU's with unlocked multiplier (or any other that allows to reach max clocks without using max mult)? I have i7 980 (not X) and Rampage 2 Extreme MB that allows to use TB mult forced. Using max mult and bclk will be 26*200=5200MHz that is unreachable. Should I use max mult or bclk or there is some mix that grands more frequency\stability?

2) Previously I had i7 920 and I managed to OC my mem with 1600 stock clock to 2Ghz. Should I try to use these OC settings with my new 980 or IMC wouldn't manage to handle it?
Hey Dart to OCForums

1) The isn't a better way per-say....just use whatever nets you the best combination of OCing between the CPU & memory

2) The Gulftown IMC should be able to handle DDR3-2000 no problem

BTW - the most recent version of my guide is here:
Dartmaul's Avatar
1st of all - thank you a lot for such useful guide!

I've made everything step-by-step and I'm in few steps (I mean bclk mhz) from my target.

I'll be very thankful if You could help me with some advice.

I want my new i7 980 to run on 4.6GHz, so that's my final goal.

I have i7 980 CPU, Rampage 2 Extreme MB and KHX1600C9D3 mem (6 modules 2GB each 12GB total) 1600MHz 9-9-9-27 timings.

So my current setting are:
BCLK = 195
CPU Mult = 23
Mem Mult = 8
Uncore Mult = 18
CPU Vcore = 1.4625v
Uncore Voltage = 1.4v
DRAM Voltage = 1.65v
IOH Core = 1.2v

Mem Timing set manually following by stock memory spec.
LLC On, HT On, Virtualization Off, CPU and IOH SpeedStep Off, all power savings Off.

I also have a new water cooling system with 2 radiators EK waterblock and only one CPU on them.

On these settings I've passed 256MB IntelBurnTest with 10 loops.

After IntelBurnTest 256MB All threads 10 loops with 195 bclk and 1.5v core voltage, max temperature has reached 90 degrees Celsius.
But 1.5v is still not enough to pass the test on 200 bclk( (So +0.0375v on CPU Vcore is not enough for +5 mhz on bclk)

Should I try harder on CPU Core voltage or I've already reached my limits?

About 2GHz mem:
I've been forced to increase QPI voltage to 1.4v to pass the test on 200 bclk with 18 Uncore multiplier.
It would be bad if +400MHz on mem will require more QPI voltage (and it seems that it will)
Seems that Gulftown's IMC is much more weaker then Bloomfield's one. Or maybe my CPU is unlucky(
256MB is not a very difficult test. I'd use "ALL" instead of "256MB" and just run 3 loops (even 2 would be enough for basic testing).

But it seems you've reached the limit of your cooling for that chip. Have you already verified you have good water block mount? And what TIM are you using? Sounds like they're fine and you just have a warm chip....but I thought I'd ask anyhow.

Concerning the IMC, 12GB is more difficult, sorry I missed that. I was saying that in general, Gulftown is about equal to Bloomfiled in the IMC dept. But 12GB at DDR3-200 is above average on either platform....so you're results are not abnormal.

What if you compromise your goal a little and shoot for 180x25? That would allow you to aim for DDR3-1800, and 4500MHz on the CPU.....you should be able to hit those goals from the sound of it
Dartmaul's Avatar
Oh you mean All available memory) It would take a while.

I've also used another test method:
In the beginning I've set CPU mult to max value (26) and start increasing bclk by +5 per step with 1.5v cpu vcore.

Every time I hit the limit I reduce CPU mult by 1 until 22.
And every time I reach 4.5GHz - prime95 begins to find errors.
4.6 is the goal but instability begins earlier.

About cooling:
I have Gigabyte case with integrated liquid cooling system.
It was actually not the best choice so Ive decided to "buff" it with EK waterblock (with additional backplate) and Alphacool radiator

Don't remember the name of my TIM but I've used it with my old CPU and was pretty happy with it.

My CPU in idle state on 200*22 1.46v has only 30 degrees while MB is 38 and NB is 45. I don't think that its a cooling problem.

Actually there is a 1 big question for me:
I've tested my new CPU in many different ways and it really seems to me that it is an unlucky chip. Should I try to change it for another one? (yep I want it to run 4.6 VERY much)
It seems to me, if you are dead set on 4.6GHz, then you need to try another CPU, or increase your cooling. You could continue to try different OCing parameters, but I think you'll be dissapointed by wasting too much time and not getting anywhere.
Dartmaul's Avatar
I've already spend enough time for overclocking this chip and enough money for water cooling. There's no sense to continue.

Here is a temperature statistic after lite stress test:

Cannot be sure but it seems to me that 14 degrees difference between warmest and coolest cores is not OK.

Gonna try to exchange this chip.

Thank you very much for guidance and personal advices, they are very useful!

BTW In your guide you pay significant attention on some theoretical basics of core die and chipset architectures. It was actually the most interesting for me.
Do you plan to update your guide with how frequency voltage and temperature are depending on each other?
(I mean something like:
Increasing frequency > increases temperature > increases resistance in a conductor > reduce effective voltage etc..)
WaroQ's Avatar
Great guide, permission to copy for personal use
Permission granted
micjmac's Avatar
I am attempting to start my overclock at 150 MHz with a multiplier of 9.

All 4 sticks of RAM are DDR3 1600, but slots 3 and 4 on the SPD tab are showing a max bandwidth of 10700. Why?

Also, if you look at the memory tab, my frequency is showing as 202.5 MHz. Shouldn't this value be 450 MHz?

Lvcoyote's Avatar
Get the timings and voltage information off of the stickers applied to the memory modules, then manually set those values in BIOS. Sounds like you have the memory timings set to auto.
micjmac's Avatar
The stickers say 9-9-9-24 so I changed both channels to this. These timings were under the standard timing section. There were a lot of advanced timings, but I left those on auto.

This did not fix my issue.
Janus67's Avatar
Did you set the ram divider to give you DDR3-1600?
micjmac's Avatar
What is a RAM divider? I'm isolating my bclk and so I lowered my CPU and RAM multipliers to their lowest settings - 9 and 6 respectively. My RAM should be running at 150 x 6 = 900/2 = 450 in CPU-Z.
Lvcoyote's Avatar
You will have to set the speed of the memory manually as well, should be in the memory options in BIOS.
micjmac's Avatar
I had a feeling CPU-Z was flawed and I was right. I tried the second to last release, and the memory is showing up correctly, as is the CPU multiplier. w00t

I still don't understand why it says the maximum bandwidth is 10700 for my DDR3 1600 2x2GB RAM kit in slots 3 and 4 though.
micjmac's Avatar
Is it ok if I just keep the memory timings on auto. That is what I had it set to when I ran prime to test stability of my bclk. I'm running memtest right now with the timings on auto still.
Janus67's Avatar
It should be fine, I would just check cpu-z to make sure that they aren't a lot looser than rated.
micjmac's Avatar
Well my overclock is 6 hours Prime (blend) stable @ 3.6 GHz (= 180 MHz x 20).

Vtt = 1.10v
DRAM = 1.50v
Vcore = 1.35v

CPU-Z is showing idle Vcore of 1.312v vs. BIOS 1.35v
CPU-Z is showing load Vcore of 1.264v vs. BIOS 1.35v

Is this Vdroop? If so, couldn't I run over 1.4v so that I can get my system stable at a higher frequency, say 4 GHz since Vdroop would be keeping me under my BIOS Vcore?

I also read on another forum that increasing the CPU PLL can allow for a lower Vcore, whereas this guide says to leave it on auto. Any opinions, real life experiences with regards to this?
Janus67's Avatar
Yes that is vdroop that you are experiencing. Setting it at 1.4v in order to get a number more in line with what you want is how a lot of people handle(d) it when LLC/Load-Line-Calibration wasn't available or didn't work well.

Not sure on the PLL allowing for lower vcore though, sorry.
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