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VRM and Mosfet questions

post #1 of 8
Thread Starter 
Would running a motherboard with CPU voltage of 1.6v be more of a strain on the VRM's than running with 0.9v?

If I understand this correctly, the VRM's are basically chokes (please correct me If I'm wrong) that reduces voltage from +12v or +3.3 down to a usable voltage for the CPU. Wouldn't it be harder on the VRM's to reduce voltage to a lower point than a higher one?
post #2 of 8
Quote:
Originally Posted by *ka24e* View Post

Would running a motherboard with CPU voltage of 1.6v be more of a strain on the VRM's than running with 0.9v?
If I understand this correctly, the VRM's are basically chokes (please correct me If I'm wrong) that reduces voltage from +12v or +3.3 down to a usable voltage for the CPU. Wouldn't it be harder on the VRM's to reduce voltage to a lower point than a higher one?

With a higher voltage, comes more current. The current is what will be hard for the power system.
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post #3 of 8
Thread Starter 
Okay, so running voltages down really low (ie, 0.850 / 0.9v) can't damage the VRM's from over-restricting the voltage down?
post #4 of 8
Quote:
Originally Posted by *ka24e* View Post

Okay, so running voltages down really low (ie, 0.850 / 0.9v) can't damage the VRM's from over-restricting the voltage down?

The act of running low voltages is not stressful. That is what the system is designed to do. The other specification of each component is the amount of max current they can handle at a certain temperature before they start breaking down.
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post #5 of 8
Thread Starter 
Alright, that makes sense. Thanks for clearing that up thumb.gif
post #6 of 8
VRM are Voltage Regulator Modules. The VRM consists of MOSFETs and Chokes. MOSFET directly takes power from the 12v CPU Power connector. They regulates and supplies voltage and current according to Processor's requirement. If we say 4 phase in a motherboard then it means 4 MOSFETs with 4 chokes. All CPUs need is high current with low voltage. Each MOSFET can provide certain amount of current and Voltage.

For Example: Let a motherboard has 4 phases and each phase can provide maximum 35Ampere current (it means total 4 x 35A = 140Ampere). Now if a Processor installed in this motherboard is overclocked in such way that it consumes 200watts at 1.45volts.
Then by the formula, Ampere requirement of Processor will be = PowerConsumption / Voltage.
Ampere = 200/1.45
Ampere = ~138Ampere

The Processor will want to take 138ampere from MOSFETs. But we know that maximum current supply by the motherboard is 140ampere and the required 138ampere by Processor is very close to the maximum value of MOSFETs. This condition generates maximum stress and heat on the MOSFETs. If you dont have enough cooling for your MOSFETs then they will die. Increasing only CPU voltage at a certain CPU frequency only makes the CPU hot. But as you increase frequency, the current requirement of CPU increases with load.
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post #7 of 8

Each phase usually has multiple MOSFETs attached: a high-side transistor, a low-side transistor, and a DRIVER chip (sometimes another regular transistor although that is a quality compromise).   Overloading the MOSFETs' transistor capacity and leaving them without cooling can both cause problems.  When you leave MOSFETs without cooling, obviously... they heat up.  They're active transistors and very fragile; when MOSFETs run hotter, they do not supply/convert as much power, reducing their potential and narrowing the gap between maximuim supply and processor power consumption - a.k.a. point of likely failure.

post #8 of 8
Thread Starter 
Thanks for posting that, sumitalian and xd_1771. Very simple and easy to understand. + rep thumb.gif
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