power requirements for 8800 series under load?

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power requirements for 8800 series under load?

Post by shadestalker » Mon Nov 10, 2008 7:53 am

Vijay's blog mentions power requirements for 8800 series cards running the GPU client:
We've been told that 8800's require 600W power supplies, but we're finding that even a little bigger (eg at least 650W) is important to leave some room for error. We are working to see if there is some way to detect this issue in software, but for now, if you're getting EUE's on the NV GPU client, this is something to consider.
This is news to me. I've run the client on my 8800GT using a Neo HE 430 PSU, and the only problem evident to me is the whine from the video card. Can anyone clarify, debunk or otherwise expand on this?

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Post by Elvellon » Mon Nov 10, 2008 12:24 pm

The GPUs' Thermal Design Power is from 105 W (8800 GT, probably less for 8800 GS) to 185 W (8800 Ultra). NVidia apparently recommends a 450 W power supply for a GeForce 8800 GTX.

The blog says that "this core had code optimizations that drove the GPU so hard that it would draw a lot more electricity", but I wonder if nVidia's way of calculating TDP permits stressing the GPU beyond it.

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Post by jhhoffma » Mon Nov 10, 2008 1:25 pm

Check my sig.

I'm running a 8800GT on a Earthwatts 430W and while the fan ramps up, it's because of the temperature not the load. I'm pretty sure I wouldn't have a problem running my gaming system with my Seasonic S12-330, but that's happy in my HTPC.

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Post by tehcrazybob » Mon Nov 10, 2008 2:11 pm

The power supply recommendations on video cards are based on the power supply ratings provided by the manufacturers of the $5 power supplies bundled with computer cases. Various white-box, stamped-steel units are...optimistically rated, and are liable to release the magic smoke or even catch fire if they're asked to deliver anything near their rated load for more than a few seconds. To get around this issue, video card manufacturers routinely recommend a power supply with roughly five times the required capacity.

A high-quality power supply actually will deliver rated capacity for extended periods of time. Conveniently, pretty much all cheap power supplies are also loud, so anything suitable for an SPCR computer is going to be pretty capable. If you've got a proper power supply, then you'll be pleased to know that, in normal usage, an 8800 GT won't draw more than 80 watts, and even the mighty 8800 Ultra can only burn through 140 watts. This might go up for Folding, but I doubt it'll even hit the TDP mentioned in an earlier post. Most 8800 users, even those with an Ultra and a quad-core, would be just fine with a 300-watt PSU. Even a money-no-object overclocked quad core/SLI insane computer will struggle to pull 600 watts.

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Post by aristide1 » Sat Nov 15, 2008 7:56 pm

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Post by cd8uk » Thu Nov 20, 2008 1:02 am

I'm running 2 x 8800GT 256MB @ 719core/750mem (each passively cooled by an accelero s2) and a Q6600@2GHz@0.9v all off an Enermax 385 Pro 82+. The total power draw under load (2 x GPU2 and 3 of the Q6600 cores assigned to SMP) is ~225w. This figure may go up a bit with the newer more intensive WUs but I haven't checked the draw recently.
So, in my experience, an 11,000ppd machine really doesn't need anything more than a quality ~400w PSU.

As for the GPU whine, a little bit of blu-tack on the GPU's "no PCI-E power cable" speaker reduces the squealing noise substantially.

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