Actual power requirements for GPU’s

[constant42]

I have a GTX 660 for which the only power requirements I can find are 24A on a single +12V rail and 450W total PSU capacity. I’m just trying to figure out where these numbers come from. All of the reviews I’ve read for 660’s show power consumption peaking below 150W, and the TDP of the card is 150W as well. This would all imply the actual needs of the card are more like 15A on the +12V rail.

I have a 300W power supple with two +12V rails with 18A on each. Why wouldn’t this work? (The peak power usage for my whole system, as I’ve measured at the wall, is around 200W.)

I’m currently using a 550W supply on this computer and it is working fine, so I’m not planning on switching the PSUs. I just want to know if it would be possible to use a much smaller on and if not, then why?

Thanks!

 

[3DVagabond]

We need to know the rest of your system specs and if you O/C anything. What brand and model psu is critical.

 

[constant42]

Hi, thanks for the reply.

System specs:
Motherboard - Asus H87m-e
CPU - Intel i5 4570
GPU - MSI GTX 660
HD - 1 tb seagate
SSD - Samsung 840
PSU - Cougar CM 550W and BeQuiet! L7 300W

No overclocking (other than the factory overclock of the GPU, which is something like increasing the core clock from 980 MHz to 1030 MHz).

 

[zir_blazer]

The reason is that nVidia and AMD likes to tell you what is the recommended Power Supply for the ENTIRE system and not just the Video Card. Its very misleading if you ask me.

 

[constant42]

Yeah, that makes sense that they are giving the recommendation based on the entire system requirements. Seems kind of a bad idea though, since they don't know what other components will be there. Why not just give the actual minimum power requirements and let people easily tell if the PSU will meet that.

Seems like power requirements are generally way over exaggerated in general though. Everything I read about the components going into my system recommended 450+ watts, but I've never seen it get over 270W, and that's at the wall (as opposed to the DC power coming out of the PSU, which I assume is 10% lower or so).

I might still try this 300W PSU just because I can't find any real reason why it wouldn't work.

 

[coffeejunkee]

I think the Bequiet will work, but the recommendations are just a general guideline and also have to take into account older and bad quality psu. Older psu's usually have much more power on the 3.3 and 5V rails, so an old 450W psu may only be able to deliver 300W on the 12V rails. Bad psu's just lie about the amount of W they can deliver.

Then there's the multiple rail issue. Your 300W psu claims to have 2 18A 12V rails but if that was true it would be able to deliver (12 x 18) x 2 = 432W on the 12V alone. If you really want to know, check reviews where they measure power use of the card alone, like TPU.