I suspect pulling the power on the GPUs might just make the system crash, if not I bet they'll still pull their idle power through the PCIE slot.
On a separate note, I think something's gone astray with my maths, I'd previously estimated that the DC draw from my old PSU was 115w, yet my rig is now pulling 112w from the wall! Unless my PSU is over 100% efficient, lol, then I've messed up somewhere......ah no, I remember now, the 1TB HDD died, so I removed it and didn't replace it, I think that cut power usage by about 8-10w, IIRC. And my calculations were based on the power draw with the 1TB being installed & a 650w Platinum PSU.
I'll start over. With my old Corsair TX650, wall draw only running Rosetta was 129w. An 80+ basic rating should mean at least 82, 85, 82% efficient for
230v at 20, 50 & 100% load.
The 129w wall draw would translate to about 106w DC output, (assuming 82% eff. at this ~16% load. You'd think it'd be less at that load, but apparently
this review of the TX650 shows that it can still hold 82% eff. @~14% load, and that's at 115v!, hmm.....).
A Platinum rated 550w PSU at 230v should have
92, 94, & 90% efficiency at 20, 50 & 100% load.
So a 106w DC load (19%, so ~92% eff.) is about 115w wall draw, (pretty close to the actual figure
). That's a 14w power saving.
With the TX650 the GPU loaded (+10T CPU) wall draw was ~260w, less 10w for the removed HDD, so ~250w would work out to about 209w DC output (~32% load, so estimating 83.5% eff).
A Platinum 550w PSU @230v with 209w DC output (estimating ~93% eff. at the 38% load) should give a wall draw of 225w, a 25w saving.
So assuming 9 mths CPU crunching & 3 mths of combined gaming/GPU crunching per year 24/7, and my electricity unit charge is 13.44p/kWh, that's a saving of £12.33/9 mths + £7.35/3 mths, a total of £19.68/yr. The Seasonic PU 550 cost me £115 (incl delivery), so it will pay itself back in ~5yrs 10mths at current elec prices (which will likely only go up, cutting the payback time). Just thought, as the actual CPU crunching power reduction is 17w, so an extra whole 3w
, it's actually saving about £3.53/yr on top of the above calculation (a total of £23.21/yr), so that changes payback to just under 5yrs
.
Not quite as good as I originally thought, but still worthwhile as this particular PSU with it's 12yr warrantee is EOL & will shortly be unavailable new, also the prices of the slightly lesser Seasonic PX 550 (Focus Platinum) are virtually the same atm and it has a slightly shorter 10yr warrantee (and higher prices for the EVGA P2 650, the only other similar power rated Platinum PSU with a 10yr warrantee).
Btw, in doing all this I discovered that I'd made (another) maths error at my original OcUK post, I had lumped 12mths/yr of CPU crunching on top of 3mths/yr of GPU crunching! Corrected now, which obviously pushed up the pay back time (by about a year).
Have I made any maths errors this time??lol
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