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Thread: Info about motherboard VRM's and powerphases.

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    Default Info about motherboard VRM's and powerphases.

    I have decided to post this because I have once faced a VRM blowout problem, so this thread is meant to help you understand the consequences of getting a cheap mobo.

    Alot of us are drooling with 125 watt cpu, overclocking it like crazy all on a cheap mobo with lower power phases.

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

    VRMs on certain platforms

    On AMD 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 LGA1156/LGA1155 phases are arranged as, for example: 4+1+1: 4 phases for CPU, 1 for integrated graphics, and 1 for memory controller. On LGA1366, phases are arranged similarly to AMD, but channels are usually in different denominations.

    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, or 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.

    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 1 or 2 transistors and 1 driver (or third transistor) 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, but if there are more phases and therefore less power going through each mosfet, it's not as hot, you should be safe even without heatsinks depending.
    • 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.



    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 motherboards cheap out and simply add a third transistor there. This is not as reliable.


    • Biostar (on newer boards), Gigabyte, DFI and ASUS, and ASRock (on newer, higher end boards) usually have the best VRM quality. Though the VRMs aren't necessarily always low RDS, etc. with them, I've found they usually have much better VRM quality and adequate ratings.


    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 these ratings are performed at stock speed and with AMD's stock cooler. At stock speed you are within that TDP limit and with the stock cooler some air gets to the mosfets and cools them. When you overclock (usually with a tower cooler), you're then exceeding these limits, which may bring additional heat and instability into the VRMs (fixable with MOSFET heatsinks). 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. 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. On the other hand, there is not one single situation I have seen where an 8+1 or 8+2 has blown.


    What to do if you suspect your VRMs have failed
    1. Check for visible damage (blown caps, missing parts from mobo, burn marks)
    2. Use your sense of smell (if they blew it'd be pretty obvious to the nose)
    3. Put out the fire! (If there's any)
    4. Run standard troubleshooting procedures to make sure it's not anything else (i.e. the power supply)
    5. Try testing the motherboard with the 24-pin plugged in but without the 4-pin/8-pin CPU power plug
    6. 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.


    For intel x58 platform, I recommend a motherboard with atleast 6 phase power and as for AMD platforms, for CPU's that are above the 95W TDP, I would suggest you a minimum of a 4+1 power, look for brands such as Gigabyte, Asus, ASrock or Biostar.
    I would avoid MSI at all costs, they have a history of vrms popping, dont come in arguing about their "military class" cus its all BS. Even the GD 70 only has a 5+1 power.
    Also remember, the more the power phases, the better overclock-ability
    FTW!!!!!!!!!!

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    Default Re: Info about motherboard VRM's and powerphases.

    Good article, but one thing. More phases isnt always better. A good 4+1 phase PWM can match a 8+2 phase PWM, depending on the specification of the chokes. However, it is usually a given that 8 phases are better than four, unless its MSI who usually go with higher specced chokes but lower phases.

    Hate the marketing from GB/ASUS etc. 20 phases? I mean seriously? Couldnt you acheive the same damn thing with 10? Pointless.

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    Default Re: Info about motherboard VRM's and powerphases.

    20- 30 phases are for people who would probably be exploring the world of LN . But yeah its more of a gimmick rather than anything, besides the 8 phase mobos arent really 8 phased, they are split 4+1 4+1 = 8+2.
    True that what your talking about, but I have heard horror stories of vrms poppings, so I kinda went back to stock from 4Ghz, since Im currently using a gigabyte 880 GM Udh2, which has 4+1 pwm w/o HS
    FTW!!!!!!!!!!

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    Default Re: Info about motherboard VRM's and powerphases.

    Next I would like to see someone giving a detailed tutorial on cooling gpu vrms rep rep to both of ya! Dang good article!

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    Default Re: Info about motherboard VRM's and powerphases.

    Well the GPU VRM's are cooled with the heatsink of the GPU . But yeah if you Mobo doesnt have heatsinks for the VRM you could always add mosfet heatsinks and thermal pads, they are readily available at the stadium.
    FTW!!!!!!!!!!

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