Alright so I got a kill a watt and took some numbers
Power Off - 1.3W
Idle (Linux - GPU at 700MHz) - 300W at the wall, assume 83% efficiency i.e. 249W
Idle (Windows - GPU at 900MHz) - 317W at the wall i.e. 263W
Folding in linux - 500W at the wall i.e. 415W
Linx in Windows - 530W at the wall i.e. 440W
BFBC2 in Windows - 660W at the wall i.e. 550W
So yes as expected gaming is the worst case for total power usage and the PSU is really stretched.
The CPU loaded to idle delta is 177W
- The delta between windows and linux idle power (14W) can be attributed to the difference in gpu voltage, this let's us roughly estimate gpu power. In windows V= 1.0875V, in linux let's assume it's 0.1V less, I can't remember exactly what the default is. Therefore total gpu power in windows = 14W*1.0875/0.1 = 153W
- I also turned off all my 11 fans and this cut power by 18W
- Let's estimate the two mechanical hd's as using 10W total
this leaves 82W to split between CPU, motherboard, memory, raid card and water pump.
It can be fairly safely assume then that most of this 82W is coming from the same rail as the CPU. Therefore total power on the CPU rail = 82W + 172W = 254W = 21.2A
- Now let's sanity check this with the BFBC2 result, normally it seems to use about 38% of the cpu, so we could assume therefore that the cpu now uses an extra 38% of (440-263) =67W in comparison to idle.
- The BFBC2 to idle delta is 548-263 = 285W, and therefore the increase in gpu power usage should be 285W-67W = 218W, adding this on to the GPU idle estimate gives a total loaded gpu power usage of 371W or 31A.
- This seems too high given that the rail is only supposed to handle 25A, so let's modify our GPU idle estimate, otherwise the system should be crashing during gaming not when stressing the cpu
-Let's assume that our system is perfectly balanced as this is realistically the maximum load the gpu could be i.e. that each rail is really capable of the average of the two estimates i.e. (254+371)/2 = 312.5W, this would mean a reduction in our idle gpu power usage estimate of ~58W i.e. 95W of idle GPU, this doesn't seem too far fetched. and is perhaps a better estimate.
- Of course the crash happens when the cpu is stressed not the gpu, so if anything the gpu idle power should be lower and the cpu rail higher. But even at this "best case" scenario for the CPU rail it's pulling 312.5/12= 26A which is over the 25A each 12V rail is supposed to handle. Of course given that the system won't be perfectly balanced It's likely that this is in fact trying to pull more than 26A on a 25A rail and the PSU is saying no.
So yes this gives me a scientific-ish reason to replace the PSU then see if the problem is still there!