Hello. I have posted this elsewhere, but thought you all might like to see it as it'd be of benefit to anyone regardless of team.
I did a little experiment to see how much power could be saved on machines that are candidates for conversion to the GPU client, but it's applicable to most machines.
The machine tested is an Athlon 64 2.0ghz Socket 754, 256mb RAM. It's a marginal folder on most Gromacs units, and only does a little better on Ambers, so I gave consideration to swapping it's motherboard out for one that's PCI-E compatible and adding an used X1900XTX card.
Folding a P2124 unit, 2.0ghz. 113w used.
Underclocked to 1.2ghz 101w used.
Underclocked to 1.0ghz 97w used.
Normally underclocking it to 1.0ghz would result in much longer frametimes, on the order of twice as long. But since the GPU client isn't so picky as to the speed of the processor supplying it...
Undervolting the processor: left at 1.0ghz, 200FSB x 5 multiplier. Stock volts is: 1.45v.
1.4v 91watts used
1.35v 90 watts used
1.3v 88 watts used
1.25v 86 watts used
1.2v 84 watts used
1.15v 82 watts used
1.1v 81 watts used.
I didn't take it below 1.1v due to dimishing rate of return.
So for a dedicated GPU machine, I went from 97 watts to 81 watts by undervolting. Savings of 16w. Really I went from 113 to 81, with no real change in utility for the GPU client most likely.
It appears to me that those folk with machines capable of running the GPU client, faster than 1ghz, might realize some energy savings by slowing down their processor to 1ghz and underclocking it some. Why spend money on power if it isn't necessary?
Final report on this system with an ATI X1900XTX and GPU client.
Here is some data, and I'll let those of you more skilled at data analysis have at it.
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).
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
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).
As a side note, before I did this round of testing, I purchased an Antec 430w high efficiency power supply and tested it with the system still set up for CPU Folding. Power useage dropped from 113w to 97w. This is from an older Antec power supply rated at about 70% efficiency to the claimed efficiency of around 83% with the new one). See here: http://www.silentpcreview.com/article684-page1.html