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About VRMs & Mosfets / Motherboard Safety with 125W+ TDP processors

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xd_1771 [OCN]

New Member
Jun 23, 2011
Vancouver, Canada
You may discuss this matter here or join me at the original article and discussion on overclock.net :)

A member suffered a mere 44 minutes before I wrote this article :(
But seriously, what's the big deal with VRMs, mosfets and power phases...

Oh yeah, they're a pretty big deal indeed.

Well, the majority of you AMD users are drooling on CPUs with 125W or similarly high TDP and overclocking them like you were beasts.
The majority of you also don't need expensive boards with features and like to cheap out by getting unreliable boards often with low-end cheap VRMs, i.e. a cheaped out 4+1 on AM3 or a cheaped out 6 phase on LGA1366.
Why do you see me often going OMG IT'S GOING TO BLOW UP LOCK THOSE CORES NOW or STOP, GET ANOTHER MOTHERBOARD AND NOT THIS ONE? Because it's simply not safe. Many of those boards really aren't even at the best value either! Usually at certain budgets (i.e. $80-100) you could get better boards with better VRMsfor the price too. Anyways, I'm tired of waving my arms and screaming at people about mosfets/VRMs in every related thread I see (actually I feel this is somewhat starting to ruin my reputation on here :() so I've decided to finally complete my write up. A local PSU guru once said...
VRMs are power supplies just like your system PSU. All the same dangers apply.

So anyways, let's answer some questions.

Let's simplify things and start with how VRMs work:

Okay, what is a VRM system anyway?

The VRM is the term for usually the entire area to the left of the CPU socket, containing the PWM controller, MOSFETs, chokes, and respective channels.
  • What is a mosfet? A MOSFET (Metal Oxide Field Effect Transistor) is a part of the voltage regulator module usually to the left of the CPU socket. The MOSFETs themselves are transistors that converts the 12V voltage into the VDIMM that the CPU uses; these are all active transistors so this is the part that gets hottest. This element is crucial because it pretty much does all the power conversion and generates the most heat, and are the most fragile in a VRM system. Usually if MOSFETs are heatsinked it is better and if they are active cooled by fan it is even better, but if there are more phases and therefore less power going through each mosfet, it's not as unsafe and unheatsinked operation may be safe to a point.
  • What is a phase or channel? Basically the more phases you have, the more reliable operation because power is split between more phases; the more phases may be smaller, but nevertheless this is much more reliable. More phases/channels is better. Such bigger phases (i.e. 8+2) can be only found on ATX boards usually.
  • Is it easy to tell how many phases there are on a motherboard? Yes. See those big black squares called chokes? (They're inductors, boxes containing coils that basically help filter and limit the current). Count them. If you see 10... usually means an 8+2. 5... usually a 4+1. Sometimes there are different combinations.
  • The entire process is controlled by a thing called pulse-width modulation, which helps stabilizes/cleans up the bulk of the power going through. Now to be honest that's something I don't really know too much about, but it's not really something looked at too often either.
  • The type of CPU connector (4/8-pin) does not have anything to do with the VRMs - you could have 8-pin + 3+1 phase or 4-pin + 8+2 phase. The 8-pin CPU power connector vs 4-pin is not important when you consider the amount of power the connector can deliver, but 8-pin connectors usually results in more voltage stability and less vDroop. vDroop can make it tougher to overclock. Just something to consider.
  • VRMs also have a play in overall system power efficiency. VRMs display similar characteristics to a power supply. They also have an efficiency level; a larger VRM system (i.e. an 8+2 phase system) would be more efficient at converting the input voltage to output voltage and have less waste power & heat, similar to an 80+ rated power supply. This will also result in less amps being pulled from the power supply - and as a result, less heat from there and less chance of failures.

Types of VRM system designs (under construction)
  • 3-transistor designs/4-transistor designs/anything without a proper "driver" chip - wherever proper driver chips may be replaced is a cost-lowering scheme, and results in inferior MOSFET quality and operations. Many low end boards or respective manufacturers will do this.
  • Driver MOSFET (DrMOS) - DrMOS is the combination of the driver and the MOSFET transistors into one chip. They are known to run cooler, and VRMs can be constructed to become smaller and more efficient this way. However, DrMOS are usually more fragile and have been known to fail a bit easier than quality transistor + driver designs at very high voltages/TDP load.
  • Digital PWM - PWM signal to control the VRMs is digitally modulated. This may allow for more stable voltage delivery (i.e. no vDroop).

VRMs on certain platforms
  • On AMD AM2+/AM3 systems: split power phase. Usually this means the majority of the phases actually bring power to the CPU, and that auxiliary phase powers the integrated memory controller/IMC. This is why VRMs are advertised in phrases such as "4+1" or "8+2" rather than simply 5-phase or 10-phase.
  • On Intel LGA1156/LGA1366 boards this is similar
  • On Intel LGA1156/LGA1155 boards with chipsets that support the integrated graphics, the phases are arranged as, for example: 4+1+1: 4 phases for CPU, 1 for integrated graphics, and 1 for memory controller. On LGA1156/LGA1155 boards without integrated graphics support (i.e. P55, P67) and on LGA1366, phases are arranged similarly to AMD (i.e. 4+1, 6+2, etc.)
  • On AMD's new Socket FM1 (Llano processor with CPU & iGPU) it works similar to LGA1156/1155 with integrated graphics enabled.
  • Older boards (i.e. before AM2+, LGA775) do not feature split power phase; the channels are not separated for certain items such as memory controller because they don't require a different voltage or more power yet, or the memory controller simply did not exist on CPU. Boards are advertised as such: 3-phase, 6-phase, etc. The VRM components were usually somewhat more separated on these older boards, this actually helps since the heat of one area doesn't spread as easily to the other. The memory controller is on the Northbridge on FSB-based platforms such as LGA775, for which power is taken from the main 24-pin connector.
  • Memory (RAM) power is always taken from a separate VRM system linked to the 24-pin connector, not the CPU VRM system.

My CPU speed is throttling even if it is stone cold!

Over Current Protection (OCP) is something I have recently been examining. This is a protection feature against VRM overheating/overlaoding. I believe it is a crucial feature on motherboards today, because this is the function that will protect your VRMs from a catastrophic failure. This is why I have never seen ASUS boards fail even if people take a lowly 3+1 ASUS boards and try to overclock a Phenom II x6 on it; ASUS boards normally always feature OCP technology. OCP can work in various ways; one of the ways it works is it downclocks the CPU speed & voltage - via cool'n'quiet or it's own function - if the VRM temperatures are detected as too high (similar to if CPU temps are too high), until they can recuperate and lower again. As a result, it can work against you. This is also how ASUS gets away with rating a few select 3+1 phase AMD motherboards at 125W, though at times the OCP may kick in too often at load even at stock speed/stock cooler and the rating would've been slightly improper for the board (there is no 3+1 phase board ready for 125W processor). Another common way is a full board shutdown; if MOSFETs are overloaded suddenly to the point where immediate shutdown is needed for protection (i.e. beginning an OCCT run on a 3+1 power phase on a Phenom II x6 OC'ed and at 1.5V), then OCP will kick in and the board will shut down to protect itself. Some boards will do this past a certain point. Others don't. OCN members and I have found that most recent MSI AMD boards feature no over current protection, and this is likely why a majority of the catastrophic failures in the horror stories list are MSI boards. At the moment I and others have been trying to find out which brands/specific motherboards do use over current protection, and we are listing them down for future reference. Once that is done, take it at heart to purchase a board with OCP for your own safety and for the best confidence in overclocking.

Regarding phase count & why this is not necessarily important

Now, does amount of phases have everything to do with a motherboard? Usually, but this is where brand name gets taken into account. For example, The majority of 2010-released MSI AMD motherboards with 4+1 phase or similar, heatsinked or not, were far from good quality. However, take the Biostar TA890FXE, it comes with a similar 4+2 power phase. Completely rock-solid. Now, mosfet quality can be hard to understand. But it really usually only comes down to two very important things:
  1. Smaller mosfets usually means low RDS (on). Low RDS is much more efficient and cooler
  2. You can see that mosfets per channel are usually in groups of 3 or 4. Usually on a good quality motherboard you will see 2 primary transistors (mosfets themselves), and one or two slightly smaller transistors nearby called MOSFET drivers. Some motherboard manufacturers may choose to lower the cost on some mtoherboards and instead of a proper driver use a third transistor chip. This is a sacrifice of quality & reliability.
A lot of people complain that their boards are rated 125W-140W and it's still safe to run that processor on that board. Not that you should take these ratings with a grain of salt, but you should be reminded that motherboards are ratified at stock speed and with the stock cooler. At stock speed you are within that TDP limit and with the stock cooler, air blows past the heatsink fins and onto the board, so some air gets to the VRM area for cooling. When you overclock, you're then exceeding these limits, which may bring additional heat and instability into the VRMs (fixable with MOSFET heatsinks). Overclocking is usually associated with aftermarket heatsinks, many tower heatsinks that blow over the motherboard; this removal of VRM cooling may significantly increase chances of catastrophe. At least 70% of all VRM failure incidents happen with aftermarket CPU cooling installed. Usually heat is what causes the majority of problems with VRMs, making power delivery unstable and potentially causing eventual failure. MOSFET/VRM heatsinks may help, and some boards allow you to monitor VRM temps (i.e. TMPIN2 on HWMonitor on my board - for your board it may depend, TMPIN2 may exist or may not at all and it may not even be VRMs). Though different VRM systems may be rated for temperature differently, ideally the temperature should be the same as the CPU load (i.e. my VRMs load at around 60, with my CPU tagging along at slightly lower than that).

Remember, phase count can still matter. Most of the culprits for VRM failures are the lower end 4+1 phase and 3+1 phase motherboards that aren't equipped to handle processors that consume lots of power and may be overclocked. There have been a few odd occasions where a very high quality 4+1 phase motherboard has blown with an overclocked (or even stock) 125W or other high TDP processor. Of course, there have also been (very few) recorded situations where motherboards with higher phase count (8+1/8+2/etc) have blown.

And now for the epically humongous and startling grand finale...
[CLICK HERE] to view a long list of confirmed VRM failures
^^^^ And that would be all the VRM failures/situations I have ever found compiled onto one extremely long list. Honestly, there's so many on here that it's not even funny any more. When I say "don't make me bring out the horror stories"... I'm serious, don't make me bring out the horror stories.

In conclusion... as a good basis I usually suggest or buy boards with reliable VRMs and cooling, according to the CPU TDP. For 125W, as a rule of thumb I usually stick to an 8+2 or otherwise smaller but quality power phase. Not that 4+1s are bad, quality ones with proper cooling can actually handle overclocks on high TDP processor; you just have to be a bit picky and choose the right board. Some tips for doing that are above :)

Board-specific VRM info:

A list of all AMD motherboards with detailed VRM information including quality/amount of phases can be found here.

So what do I get and what do I not get?
Well, assuming you read the whole article, if you are planning to buy a motherboard, this is what you do:

AMD Platforms on high TDP (~125W) processor (includes unlocked CPUs):
Remember, you can refer to the AMD Motherboard VRM info article/table for info about specific motherboards (see link above)
  • Look for a minimum 4+1 phase on the board. Higher is better though.
  • Be SURE it is of quality; if so,
    • preferably low RDS
    • A proper 2-transistor/driver design that is not cheaped out
    • On a brand that is not known for failures.
    • If you are overclocking with a high TDP processor and a 4+1, consider MOSFET/VRM cooling a MUST. Some boards may already have this. Fewer phases will overheat much easier.
  • If you have enough budget to get a board with a better, larger VRM system (i.e. 8+2 phasing or similar) and/or room for larger board size (ATX usually has better VRMs than mATX), there is not much need to worry.
    • Cooling is no longer as big an issue because the larger amount of (smaller) phases run cooler over a larger area
    • Most 8+2 feature at least a quality 2-transistor/driver design nowadays.
Intel platforms on high TDP processor:
The rules are similar, however do pay attention to the overall TDP of the majority of Intel processors. Some platforms set a 95W max, this consumes less power and may require less phases for good functionality, even overclocked.

What VRM cooling will do for you
VRM cooling is an important part of keeping VRM temps down. VRM cooling is usually placed on the MOSFETs, active transistors that are the most fragile and the hottest. Often the VRMs get little to no air so as much heat radiation as possible would be best. What I recommend you do in terms of cooling the VRMs and running a high TDP processor:
  • Add any sort of VRM heatsink such as MOS-C1 if there isn't already, especially on 4+1 boards even with quality
  • Add active cooling. A small fan, or Spot Cool, will do. While most VRMs will run safe with VRMs and no active fan cooling, huge temperature drops have been shown from even really weak 40MM fans that don't push much air.
  • Improve on case airflow. i.e. add that top fan in the slot above the VRMs (heat naturally dissipates upward).
OCN member mdocod has found that as of 3 March 2011, at least 71% of the VRM cooling failure incidents in the compiled list of horror stories have happened on a cooling that deviates from stock cooling. This value may be higher due to the amount of situations where cooling was not described.

"Stock" CPU cooling is designed to blow down onto the motherboard including VRMs. This includes: tower cooling, any sort of water cooling. Remember, TDP rating on all boards is done with processors at stock and with stock cooling. That means your 4+1 phase (on AMD platform) may actually be fine for a 125W processor with stock cooling & stock speed, but deviate any one of these and you're on your own.

A few last notes:
  • Some of you may get word about 8+2 phase basically being a 4+1 phase and not being true 8+2 phase. This is actually true, a lot of what I usually call 8+2 anyway just for simplicity, is actually something called 4+1 split; there are 4+1 channels, but the components (i.e. chokes, mosfets) are split as if they were an 8+2 phase; this is quite close enough to the quality of a true 8+2 phase on a reliable PWM controller. My own motherboard (the Gigabyte MA790XT-UD4P) would be a good example of this. Once again I usually call those 8+2 phase anyway just for simplicity.
  • My list of horror stories grows constantly... feel free to check back for updates every couple of weeks or months or so!
  • Concerning Driver MOSFETs where the transistors & mosfet drivers are merged into 1 big chip... do they mean quality? Not necessarily. Take for example: MSI's 790FX-GD70 and 890FXA-GD70. They both have these new Driver MOSFETS (DrMOS) that are supposed to run much cooler and better, and yet they still are known to blow up at high voltages & high TDP processors just as with other MSI AMD motherboards released in 2010. This is probably a problem somewhere else then, i.e. the chokes, or PWM controller.
  • I've been planning to do a write-up like this for while, but I probably made a lot of mistakes writing this... be sure to tell me if so :p
What to do if you suspect your VRMs have failed
  1. Unplug everything/cut power to the PC
  2. Check for visible damage (blown caps, missing parts from mobo, burn marks) [this might not always be the case]
  3. Use your sense of smell (if they blew it'd be pretty obvious to the nose, but it might smell really bad)
  4. Put out the fire! (If there's any)
  5. Run standard troubleshooting procedures to make sure it's not anything else (i.e. check the power supply)
  6. Try testing the motherboard with the 24-pin plugged in but without the 4-pin/8-pin CPU power plug. This is the ultimate dealbreaker; if the motherboard only boots when CPU power plug is unplugged (though it obviously won't POST), you sir have a VRM failure on your hands.
  7. Report it here! The more VRM horror stories are in the posted horror stories list, the more aware this can make people about this overlooked issue.
Remember, not all VRM failures are visible and involve fire & explosions! Sometimes they can take other parts with them, sometimes not.
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Sep 15, 2006
about time somone wrote that.
hey my processor is at only 52* C , I got wonderfull cooling
just ignore the fact that my regulators are at 108* C , cause that dont matter none :)

for me and my more minor systems and minor voltage increases, I only am only worried a bit about when i change to a "tower" style of cooler and there is minimal air passage around those things controlling the power to my CPU (which is intel not amd)
there isnt very many flat headed coolers in existance , that fit and have most of the same cooling capability of a vertical tower thng, so that sucks for me.

i did not see any misteaks, or would even know if they exist, but when you talked about the PWM and controlling mosfets, nowdays in high power stuff they basically have to be "digitally" controlled and very fast spike on/off type of switching, anything analog or inbetween and they are half on and will burn out quite quickly. any other reason that they might become half on would also do that. so you can think of a bunch of other reasons why they will turn to toast in seconds , with things like voltage supply being to low (somewhere), other component failures etc.

Also electronic gate switching being pushed to hard can take much time to fail. i see somethings they say "hey it works like that" and i say "for how long though" :-(
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Aug 19, 2012
Mosfets and Vrm's Sections!

The overall purpose of this thread and post is to inform and educate the new members! Why these Mosfets and Vrm's are important to all members.
The first post kindly explains what these important things do on your motherboard. The second post is a list of failures and reasons why and what happened and with what motherboards! I hope this goes towards some way to helping and educating the members when buying motherboards for a build. ;) :thup:

1, http://www.overclockers.com/forums/showthread.php?t=679903

2, https://docs.google.com/spreadsheet...DYyU3BOenBQRWhSdkpKejFwQzBUTXc&hl=en_US#gid=0

Please kindly leave your comments and remarks on this post!

EDIT: As you can see the thread has changed some what, so please still post as normal and hopefully this will develop into a discussion in the AMD Section. AJ.
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Water Cooled Moderator
Oct 14, 2007
Hey Ajay, I moved your post into the thread to which you linked. It's already here, in this section even. Next time you see something you'd like people to see (and you think it's relevant to current discussions) and it's already on the forum, just bump the thread. Creating a thread simply to link to another thread which already exists with virtually the same title just clutters up forum search results.


Aug 19, 2012
Sorry Hokie thanks for the heads up. AJ.

EDIT: Well looks like ive drawn a black on this one and i am feeling a bit confused, i thought it would be a good topic! But looking again at this seems more like a Dead duck all round, ah well one can only but try. So if no one is interested case closed as they say!!!
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