• Welcome to Overclockers Forums! Join us to reply in threads, receive reduced ads, and to customize your site experience!

6600 K OC Questions (CPU/Memory/Voltage)

Overclockers is supported by our readers. When you click a link to make a purchase, we may earn a commission. Learn More.


Jan 1, 2017
Hi Everyone,

First time posting here and new to Overclocking. Hi! Did some reading on other threads and learned quite a bit already. I have a few questions (specs at bottom):

I have been playing around with voltages but figured I'd finally leave on auto to see what I could get. I plugged in 4.6 GHz and got a stable OC of 4.6 GHz with memory under running at 2400 MHz (I have memory rated for 2666 MHz) with voltages around 1.35V and acceptable temps using OCCT, Real Bench, and IBT. I'd like to push my memory up to 3000MHz but I lose system stability at 4.6 GHz without touching the voltages. In general, should I leave the CPU voltage on auto or set it manually? Is running at say, a steady 1.35V better than leaving it on auto? I know I need to stay below 1.4 V but I do wonder because I'd like to save power, prolong the lifespan of my mobo/CPU, and reduce heat (I'm using an H80i V2). That said, consistent sharp increases in voltage probably aren't good either, are they? Should I consider adaptive or offset modes? How do those work?

Would I gain more performance if I dropped my CPU frequency and then increased RAM speed? Here's a hypothetical example:

case a) 4.6 GHz with memory underclocked to 2400 MHz
case b) 4.5 GHz with memory overclocked to 2600 MHz
case c) 4.4 GHz with memory overclocked to 2800 MHz

What would give me the best overall performance increase?

I know that memory runs on it's own voltages...if I can get a stable 4.6 with my memory at 2400 MHz, what would I need to adjust to give my memory more voltage? Just out of curiosity, what would be considered a safe voltage limit for memory? I don't plan on going crazy but it'd be nice to know.

Thanks for any constructive advice and guidance!

Mr. Gisa

(Comp specs)

CPU - Intel core i5 6600k
Mobo - Asus Z170-A
RAM - 16 GB G.Skill 2666 MHz
PSU - Antec High Current Gamer 900 W
O/S - Windows 10
Case coolers - 2 200 mm corsair air fans, 1 120 mm corsair air fan
GPU - Asus GTX 1060
CPU cooler - Corsair H80i v.2 (~130 mm rad with 2 120 mm air fans)
IT is best when overclocking a new system to do one thing at a time instead of trying to overclock everything at once. My normal order of overclocking is, CPU core then CPU cache, and lastly memory.

My suggestion is you set everything back to auto and starting working your cpu core up first. Once you find a stable overclock on that we can then work at bringing up the cache and then the RAM.

I would set your core voltage at 1.3 volts and your core multiplier at 44x. Then stress test your system with one of the above mentioned programs. If it passes then raise the multiplier one and retest, if it does not pass add 0.01 volts to the core and try again. Keep alternating this procedure until you find an overclock you are satisfied with or your temps get out of hand(Keep below 90c while stress testing). I would not advise going above 1.4v on the core voltage though. Once you do this and find where your core tops out we can then work on the other aspects of your system.
Will do. At 4500 at 1.31 V so far but will continue on until I get a stable clock at temperatures that are acceptable.
Memory is running at 2100 MHz for the testing...should I put that to 2666 (it's recommended rating) and go from there or best to just leave it at 2100 MHz until I get a stable OC?

Mr. Gisa
Configure your RAM in bios to XMP. Intel CPUs have stout IMCs so it should not be detrimental to your overclock to run the RAM a the full 2666 mhz rating and the XMP timings as well.
I normally run the ram at the lowest setting when doing my cpu overclock as I do not intend to run the ram at the XMP settings anyways so I gain nothing by running them there while working on my cpu overclock. As you are in the same boat with wanting to try and push your ram further than the XMP setting I would just leave it where it is for now. If you were intending to run it at the XMP settings then yes as Trents said I would just enable the XMP settings and forget about it.
If you wan't to test the memory first with XMP and no CPU overclock then stress test, after that overclock the CPU.
Thanks everyone for your replies and advice.

Would I really gain anything noticeable in performance if I could get my RAM up to 3000 MHz? or even 3200MHz? Would it be worth it? If not, I might as well leave it at 2666 but if so...
Faster speed memory past 2133 speed will not help daily computing. If you play games overclocking the memory past 2600 speed will not help much at all. Faster speed memory is good for synthetic benchmarking.

No very much to be gained with most apps by using high speed memory. Some very CPU intensive apps that use large amounts of memory (like file compression/decompression) would benefit noticeably but by far the most important parameter is CPU speed. A lot of games benefit a little from higher speed memory.
Thanks for linking to that video. I've seen a few others that came to a similar conclusion but hearing first hand from others is more reassuring. I'll aim for either the stock rating, or up to 3000 MHz if I can get away with it. If I can't, I'll be quite happy with the 2666 MHz rating. I was on a budget at the time of this build and I couldn't see the point in dropping another 10-15 for a few hundred MHz (plus, compatibility was an issue and finding RAM with good timings, speeds, and that was in my budget were factors).
Now to do some stress testing...
Been using OCCT quite a bit for testing, nice to see I can finally get through a 15 minute test without crashing so quickly. I tried using ASUS' 5 way optimization suite but it wasn't very solid (suggesting 4.4 GHz and OCCT/IBT crashed pretty quickly if I recall). I find using OCCT it a fairly quick/reliable way of scouting a stable overclock for the time being.
I did manage to get to 4.7 GHz @ 2133 MHz by only changing my voltage to 1.395. According to CPUID HW, voltage seemed to peak at 1.42 which makes me a little uncomfortable. Temps were barely acceptable (very high 70s) because I have an H80i V2. Maybe with better paste, a better cooler, and arguably a better chip, I could achieve 4.7 but I've decided to go with 4.6 GHz as an overclock as that is still great in my mind, lowers my voltage, helps my temperatures stay lower, and gives me a bit of room for pushing my RAM up to 3000 MHz.
Testing at 1.280 V for 4.7 GHz, OCCT just threw up an error as I was typing this, so I'll go up a bit more until I find the right voltage that can pass the first OCCT test, then do some more lengthy testing.
Lochekey, you mentioned the next step was adjusting the CPU cache. What would I need to do that? Are there are any articles about doing so for dummies, such as myself? :D
Thank you all again for your posts and advice.

Mr. Gisa
On Skylake the cpu cache is tied to the vcore instead of having an independent voltage of its own. If you are aiming for a 4.6ghz overclock at around 1.3v you will just need to start turning up the cpu cache multiplier and then stress test. You will not see huge gains by raising this so I suggest raising this until it becomes unstable and then backing down to the last stable setting. There is no point trying to push voltage to raise the cache speed unless you plan to benchmark. If you can get the cache to 44x i would call it a day and leave it at that personally.
Thank you Lochekey for your explanation. I managed to get 4.6 GHz at 1.285 (slight stability issues while doing a stress test and extra stuff on a computer) so I put it up to 1.290 just to be safe (and to give a bit more wiggle room for the other overlocks). I wanted to ask two questions:

1) with this BIOS, there are three input sections regarding the cache:
a) CPU Core/Cache Current Limit Max
b) Min. CPU Cache Ratio
c) Max CPU Cache Ratio

Should I put ALL of these to 44 and test or just b and c? I tried b and c and ran OCCT (and passed) Intelburn (even passed on very high stress test) and realbench for 8 hours last night and passed but knowing my luck, all three have to be at 44.

2) I noticed there is a TPU setting as well. I've kept that disabled, since I am just focusing on the overclocking. Should I just leave it at that or can I adjust it to phase II (water cooling). If I adjust it, will it start making automatic adjustments to other things that I do not want? I miss seeing my overclock stats on boot up and wonder if this might be beneficial too?

Almost done...then just the memory to go!

Mr. Gisa
Only b and c the current limit is just that . It's for power draw and leave it at auto. Increasing cache speed can create a need for slightly more voltage since the core and cache get power off the same source. Leave TPU disabled.
Thanks Johan45! I got the CPU Cache Ratio at 44x without any issues.
For the last step...I want to get my memory all settled in. I'd be super happy with 3000 MHz, but could still be content with 2800 MHz. I like to learn by trial and error at times, so I've been simply upping the core voltage along with the memory speeds and it's quite demanding. I'm at something close to 1.350 V just for 2800 MHz in terms of stability, but I think there is a better voltage I can change than just the Vcore one, right? Could someone point me in the right direction?

Mr. Gisa
Knowing the model # of the ram or a picture of the label would help here but you can try these settings. For 3000 try 16-16-16-36 1.35v for DDR4 is fine.
Here's some more information about the RAM I got. I should have bought it in the summer but if we could look into the future...

G.SKILL Ripjaws V Series 16GB (2 x 8GB) 288-Pin DDR4 SDRAM DDR4 2666 (PC4 21300) Intel Z170 Platform / Intel X99 Platform Desktop Memory Model F4-2666C15D-16GVR

DDR4 2666 (PC4 21300)
Timing 15-15-15-35
Cas Latency 15
Voltage 1.2V


Is there a separate voltage I can adjust just for the memory instead of the Vcore? If so, what is it called?

Mr. Gisa
Yeah it's DRam voltage most likely, usually below the VCore in the list
Thos timings I listed earlier should work without too much trouble I think, most likely at 1.2v or slightly more.
I personally overclocked my system with xmp on which was 3200Mhz so that I could get a stable overclock with my memory running at high speed than later I disabled xmp and manually overclocked my ram further. So I didn't have to trial and error with it at 2133Mhz then trial and error again later with xmp. I also just kept Core and Cache ratio the same the entire time for the most part. I can get 4.7Ghz but I don't like the voltage it takes and for my setup the best Core/Cache overclock I can hit with them together like that and still keep voltage low is 4.5Ghz/45 at 1.3v Then once I got there I manually overclocked my ram further to 3333Mhz keeping the same timings. I haven't had a lot of time since to go further with Ram but I think it was easier and quicker to overclock first with xmp on so you can find a stable overclock with higher memory speeds then disable and go further. I also use llc because I like to be able to idle at a lower vcore than when under load. So at level 7 I can idle at 1.296v and it;ll bump up to 1.312-1.328v under load. And my memory it rated at 1.35 and I have it bumped to 1.355v. But 1.3-1.35v should be safe with most ddr4.
Just reporting back about my final OC adventure.

Trying to get my RAM at anything above it's rated value has been...challenging. I've fiddled with Core Voltage and OCCT crashes quickly if I try to push the RAM beyond it's rating. Tweaking DRAM Voltage did not seem to help either. Temperatures were also getting hotter and my RAM has no cooler on the sticks themselves. I've decided to just go with the rated rating (2666 MHz) as I know I'm not going to see any significant gains by pushing the RAM that much harder. Any gains I do make at this point put more risk on my board (voltage and heat) and after multiple days of fiddling, I think I can say I am happy and done as I want to enjoy some games before going back to work next week.

Thank you to all who have helped guide me through this process. I could not have done it without you.

Now to play some games! Cheers all!

Mr. Gisa