Inspired by this thread http://forums.overclockers.co.uk/showthread.php?t=17736615, I am going to do a few experiments to settle this GPU power myth on these boards, this should also give people a good idea as to what PSU they should consider if buying an HD2900XT. Hopefully this should be helpful to some people.

I purchased one of these :-



This can Measure voltage (V), amps (A), watts (W), volt-amps(VA), hertz (Hz) and power factor (PF).

Ok so the first test I did was to get into Windows, In windows my pc idles using around 250-260w. This is my power usage at idle when you take into account I have an R600 which is supposed to be some sort of power monster even in 2d I found this pretty impressive. So i fired up Orthos and stressed for 10 minutes, throughout the whole ten minutes the power stayed at 300-308w and didn't budge. I will be doing some 3D tests when i get back on my other PC, does anyone want to take a guess as to the power my PC will use in 3d mode based on the 2d power results?, What do you think?, post up your guesses.

407.3

370

350 I would say

EDIT: I'm probably a mile off

just over 400w.

Im going for just under 400w, so around 390 I'll say , Will be using 3D Mark 06 and will monitor throughout.

420w

223.7?









Only kidding.

395

I'd say ~390w in 3DMk06, but 430w+ playing STALKER with lots of AI.

3DMk doesn't stretch the CPU much (and sound card isn't used at all) when running the 3 gfx card tests. You need to test it with something that uses the GPU and CPU at the same time (like STALKER).

390

LoadsaMoney said:

just over 400w.

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same here, over 400w if the cpu and gpu are both stressed at 100%

also
can you do some cpu testing.

use orthos and see how much power it consumes, and use snm to see how much power is then used. for all the systems i have ever used snm generated the highest heat load so i guess it will be the one that pulls more power.

Ok the 3D Mark results are in, the power usage remained between 370-400w the highest it peaked was 400w and it only stayed there for a split second this was on Canyon Flight and in the cpu tests the power usage remained around 350w. Im fairly suprised and I will do more tests with various different games to see how it affects the power usage. All in all 400w is impressive, just shows you can most likely get away with a 2900xt on a 450w with decent railage and still have a nicely oced C2D.

Cyber-Mav said:

same here, over 400w if the cpu and gpu are both stressed at 100%

also
can you do some cpu testing.

use orthos and see how much power it consumes, and use snm to see how much power is then used. for all the systems i have ever used snm generated the highest heat load so i guess it will be the one that pulls more power.

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Stressing both cores to 100% on the CPU test in Orthos @ priority 9, the power usage didnt go above 308w. It hovered between 300-308w.

interesting, so does that mean any psu with 400w on the 12v rails is good enough?

would be good to know how much power is sucked up from the 5v rails these days.

but yea as you say, something like a corsair 520 is more than enough for anyones needs.

Cyber-Mav said:

interesting, so does that mean any psu with 400w on the 12v rails is good enough?

would be good to know how much power is sucked up from the 5v rails these days.

but yea as you say, something like a corsair 520 is more than enough for anyones needs.

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Precisely, it's a shame Corsair dont do a cheaper 450w model or do they?, because even thats more than plenty . Very impressed tbh its put my mind at rest and opened my eyes anyway.

To factor in efficieny yiou need at least a 500w supply then for that power consumption. Maybe a bit more.

Very comforting to know

I did think all this "You need a 700w+ psu!" stuff was a little over the top from some sites I've been reading, but I never thought it'd be that low, means I can hold on to my Antec 500w Smartpower that little bit longer and still upgrade my video card

Cheers for the info

Dureth said:

To factor in efficieny yiou need at least a 500w supply then for that power consumption. Maybe a bit more.

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Yea but if you get an effieicent enough 450w or 500w then your spot on. If you got a totally efficient 700w it would last you forever , this does not mean any old 450w psu could run my setup, it would have to be fairly efficient.

Tom|Nbk said:

Stressing both cores to 100% on the CPU test in Orthos @ priority 9, the power usage didnt go above 308w. It hovered between 300-308w.

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Can you try running 3DMark while the Orthos CPU test is running? It still won't use the sound card, but will give us a better idea of the max game consumption.