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GPU client minimum support cpu

T

taqueso

Gawd
Joined
Mar 30, 2003
Messages
571
What is the slowest cpu that can support a GPU client without slowing it down? I imagine it varies for faster/slower GPUs, so any input on various card/cpu combinations are appreciated. I am considering pairing a X1950 pro with an althon xp @ ~1600. Would I be better off popping in a barton, or is it a waste of money? What if I went with an XT?

edit: this would be on AGP, I'm not sure if it makes a difference or not
 
Should be fine, but it'll want the entire core. If it's a dedicated folding box then I think it'll work great, if you plan on using it much at the same time, the PPD will sux0rz. :p (did I just 1337S93AK in the DC forums >.>)
 
It would be a dedicated folding box. So the GPU client will work with a slow CPU, but still uses an entire core with a faster one? It must use some kind of polling. Will PPD be the same with either CPU?
 
The primary speed factor for GPUs is the number of shaders, 48, 32, 16, which affect points by the hundreds a day. The CPU speed does have a small impact on speed, but only in the double digits per day, not triple like the number of shaders.

And get a 512 MB card if you can afford it. The lagging on 256 MB cards makes using the computer rather annoying, and buys you some longevity because the f@h WUs just keep getting bigger.

As for the absolute minimum processor, it is the slowest CPU supported by any motherboard with an AGP 4x/8x slot. Processors are not the gating factor.
 
As for 256MB cards having an issue, yes they do, with the only exception being the X1950Pro. For some reason it doesn't have that problem (heard from others and experienced myself), even on the 256mb cards.
 
Going from 500 Mhz -> 650 Mhz GPU clock speed cuts frame times by ~2 mins on my X1950xtx.
Going from 2.2 Ghz -> 2.75 Ghz C2D CPU clock speed only cuts frame times by ~5 second on my X1950xtx.

Luck ............. :D
 
If you'll read this, which I have posted elsewhere, it shows the effect of slower CPU speed on production: Strangely enough there wasn't much interest in it here, but anyways...

Using stock CPU voltage, frame time and power useage at various CPU speeds, GPU Client on an ATI X1900XTX (650core/775mem, ie, stock 3d speed). Original processor was an A64 2.0ghz 1MB Cache CPU.

2.0ghz 6:12/frame 207w power
1.8gz 6:16/frame 207w power
1.6ghz 6:18/frame 198w power
1.4ghz 6:22/frame 193w power
1.2ghz 6:26/frame 192w power
1.0ghz 6:32/frame 189w power

After graphing it all up, I found that the power useage curve dropped off sharply between 1.8ghz down to 1.4ghz, and then leveled off at 1.2ghz before dropping again at 1.0. I think 1.4ghz is the sweet spot here.

Data showing power consumtion versus increase in frame time:
1.8ghz 0% reduction power, +1.07% frame time
1.6ghz 4.3% reduction power, +1.6% frame time
1.4ghz 6.7% reduction power, +2.6% frame time
1.2ghz 7.2% reduction power, +3.76% frame time
1.0ghz 8.6% reduction power, +5.37% frame time

Next I tried undervolting the CPU. Speed selected is 1.4ghz. Stock CPU voltage is 1.45v. I ran Orthos with a simulated Gromacs work unit to avoid corrupting the GPU client work unit if there was a Early Unit End due to crashing. I know the data isn't strictly comparable, but it gives an idea of what kind of reduction to expect with undervolting.

CPU voltage power watts used
1.45 (stock) 118w
1.35v 108w
1.25v 103w
1.15v 99w
1.05v 95w

I left the CPU volts at 1.05v and started up the GPU client. No change in frame times, and it's been processing for an hour now with no noted instability. Total system power useage dropped to 166-168w (keeps fluctuating between the 2 readings). So I went from 207w to 168w (savings of 39w) with a modest reduction in production of 2.6% (766 Points per day to 747: 19ppd difference).
 
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