Why does the VRM play a large role in GPU OC over the PSU?

[turkey3_scratch]

I frequently hear it said that the VRM, and VRM cooling is most important when it comes to overclocking the GPU or the CPU. But that does not make sense to me, because is not the majority of the GPU's power supplied by the PCIe power connectors from the PSU, rather than from the motherboard? Same with the CPU, the ATX12V or EPS12V cable comes from the PSU, so what role does the VRM play when it comes to delivering the CPU and GPU their power?

 

[DarkVirgo]

The VRMs are important for CPUs and GPUs because, while you are correct in the fact that the power itself comes from the power supply, that power then has to pass through the VRMs where the voltage and power delivery to the processor itself (whether it be CPU or GPU) is regulated to keep things clean and stable. They will set the voltage at a value, and hold that value, to allow for reliability and stability, which is obviously very important for overclocking. Hope I helped.

 

[clutchc]

The VRM (voltage regulator module) contains the power transistors that deliver precision power to the GPU. Doing so, it can get extremely hot. If the power transistors are not cooled, they will burn out. The motherboard's PCIe x16 slot and the aux power connectors both provide the +12V supply to the card's circuits.

The more work done by the VRMs, the more current that will flow. The more current that flows, the more heat generated.

I have a feeling you already knew this.

 

[turkey3_scratch]

What do you mean by "precision power"? The PSU already provides clean (well, some do) 12V direct current. What other work does the VRM need to do with this? And how could power that goes through a PCIe connector which goes directly from the PSU to the GPU possibly be related to the VRM?

 

[DarkVirgo]

The power from the PSU goes into the card, yes, but it first goes directly into the VRMs where it is regulated and then sent out to power the core and such. It provides more "reliable" power to components, if you give it a value it will never fluctuate (in theory).

 

[turkey3_scratch]

Then why on earth do PCIe power cables plug into the GPU rather than the motherboard?

 

[clutchc]

What do you mean by "precision power"? The PSU already provides clean (well, some do) 12V direct current. What other work does the VRM need to do with this? And how could power that goes through a PCIe connector which goes directly from the PSU to the GPU possibly be related to the VRM?

Maybe I should have said clean regulated power. Cleaner than the PSU can deliver. The power from either the PCIe slot and/or the PCIe connector feeds the card's PCB's devices which changes the voltage to various lower levels that are required. Just like your PSU is fed with 120V AC (US) and transforms it down to 3v, 5v, and 12v DC circuits, the card's board has the ability to do the same with the +12V DC supply it receives. It is in fact a mini motherboard.

 

[turkey3_scratch]

Okay so the transistors and the cores and the shaders on the card aren't necessarily carrying 12V current? Also, are you referring to the mobo VRM or the GPU's PSB VRM?

 

[DarkVirgo]

The GPU and motherboard have separate sets of VRMs

 

[turkey3_scratch]

But why would the motherboard's VRM have effect on the GPU, rather than it solely being the GPU's VRM?

 

[DarkVirgo]

The motherboard's VRMs don't have an effect on the GPU. Motherboard VRMs go with CPU, and GPU VRMs go with the GPU.

 

[turkey3_scratch]

The motherboard's VRMs don't have an effect on the GPU. Motherboard VRMs go with CPU, and GPU VRMs go with the GPU.

That helps clear a lot of confusion up, thanks!

 

[DarkVirgo]

No problem, anytime.

~Good luck

 

[clutchc]

Good lord! lol... I thought you were referring to the VRMs on the gfx card.