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Points per Dollar


endorphiend

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Today I borrowed a Kill-A-Watt meter from a coworker to run some math on how much it will cost me to run my new rig for folding. Don't get me wrong, I'm a generous guy but I don't want to accidentally run up a $300 electric bill this month. I'm trying to maximize the points I get per dollar.

 

I have checked my math a few times, but would anyone math inclined mind checking my numbers? Note that these calculations are naively ignoring the increase in the cost for air conditioning since I'm not exactly a professional at thermodynamics ;)

 

These are the facts I used in my calculations:

 

CPU PPD -smp 8: 34,000

CPU PPD -smp 7: 30,000

GPU PPD: 14,000

GPU OC PPD: 16,000

CPU + two GPU PPD = 58,000 (this is with -smp 7)

 

Last electric bill's cost: $50 (minus service charge)

Last electric bill's usage: 686 kwh

 

These are the readings from the Kill-A-Watt meter:

 

idle....................220W = 0.220 kW

1GPU................380W = 0.380 kW

2GPU................520W = 0.520 kW

load...................340W = 0.340 kW

load 1GPU .........490W = 0.490 kW

load 2GPU .........635W = 0.635 kW

load 2GPU OC ..770W = 0.770 kW

 

My calculations:

 

Cost for one kilowatt hour: $50/686 = $0.072915

 

hour_cost = kwh * 0.072915

day_cost = hour_cost * 24

month_cost = day_cost * 30

points_per_dollar = points_per_day / day_cost

 

Cost to run each for an (hour; day; month; Pt/Dollar)

 

idle...................$0.02; $0.38; $11.55; 0

load..................$0.02; $0.59; $17.85; 57,143

1GPU...............$0.03; $0.66; $19.95; 21,053

2GPU...............$0.04; $0.91; $27.30; 30,769

load 1GPU........$0.04; $0.86; $25.72; 51,313

load 2GPU........$0.05; $1.11; $33.34; 52,194

load 2GPU OC..$0.06; $1.35; $40.42; 46,011

 

Therefore, my most efficient solution is to get 34,000 PPD for $17.85/month by running my CPU only. However for 9% less efficiency I can get 58,000 PPD for $33.34/month by running everything full steam ahead, assuming I run 24/7. Most likely, I'm going to run the CPU 24/7 and the GPUs while I sleep, which would be:

 

.67 * cpu_load_month_cost + .33 * load_2GPUs_month_cost = $11.95 + $11.00 = $22.95/month

 

And, to me, $23/month seems like a reasonable enough "donation" to a worthwhile cause. Unless my math is wrong!

 

Thoughts? Corrections? Finger wagging?

 

:foldon:

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the one thing you might have overlooked is folding kills your card. after about 2 years it's going to have to be RMA if possible. I know this isn't a downside for most but it's like a car, ever mile is a mile closer to breaking. I wonder if you can factor in the cost of cards over a length of time.

 

$400/730=0.5479452054794521 so 54 cents a day if you can't RMA it stating it will die within 2 years.

Edited by hornybluecow

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if there's a space between the two 480s then get a PCI slot fan

 

1

2

3

Currently there is no space. My motherboard has the following setup:

 

PCIe 1x (empty)

PCIe 16x (first 480)

PCI (first 480's heatsink)

PCIe 16x (second 480)

PCI (second 480's heatsink)

PCIe 16x (empty)

 

With this setup while folding on both GPU's and fans at 85% I'm seeing temps of 74 on the top 480 and 68 on the bottom GPU.

 

I'm considering changing it to the following to reduce the temps of the top GPU. If I do this, I'll try out the first PCI fan you suggested and see how the temperatures react. I'm also considering getting a powerful 120mm fan with 100+ CFM to mount in the HAF X to blow directly at the video cards. At first I was concerned about the noise -- but there's no way it can be louder than these 480's at 85% fan speed.

 

PCIe 1x (empty)

PCIe 16x (first 480)

PCI (first 480's heatsink)

PCIe 16x (empty)

PCI (empty)

PCIe 16x (second 480, there's room below for the heatsink)

 

The only reason I haven't made this change yet is that I have read the PCIe 16x slots can run at either 16x, 16x, 1x, or 16x, 8x, 8x. My concern has been a loss of performance if I move into the bottom PCIe 16x slot, although the board is designed for tri-SLI so maybe I should chalk it up to laziness :)

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