I'm not sure if this has been mentioned before, but I've heard that Active PFC PSU's make Kill-A-Watt readings inaccurate. Supposedly, connecting the PC to a UPS then the UPS to a Kill-A-Watt is one workaround. If you do this, you'll first want to connect the UPS on it's own to see it's power draw and subtract that from the total.
I'm using the same PSU and the same kill-a-watt for measuring power for all three CPU (2600k, 3770k and fx8350).
To whatever extent your concerns are true, the extent of the error should be present (and nearly the same) in all cases.
That said, I'll do the test as you suggest just to put an absolute number to it.
I tend to think that kill-a-watt readings aren't so accurate due to the nature of AC and power calculations (although they provide some rough approximations I suppose). It'd be much better and alot more accurate (by dealing with DC not AC) if we could measure the actual current in the 12V rail via current transformer or a cut in the 12V rail with a current meter..
Subscribing to this thread, very interested in the outcome and the findings regarding power consumption!
Kill-a-watt claims an accuracy of 0.2%.
My PSU is the Corsair Professional Series Gold AX850 (
cmpsu-850ax) which has ~89% efficiency across much of the output range, and only varies by about 2% efficiency across the entire range:
(^ Corsair's technical data)
As you can see, we are looking at loads on my PSU that range from ~220W to ~380W, meaning the PSU efficiency is ranging from ~90% to ~91% across these tests.
That means the DC losses are at most 10%, 288W (±0.2% = ±0.6W) at the wall means the system (sans PSU) is really drawing 260W. And at idle the 87W at the wall means the system (sans PSU) is really drawing 78W.
That still means we have a situation here in which the loaded FX-8350 at stock conditions (stock HSF, stock Vcore, etc) results in 180W more power consumption when running LinX versus when the system is sitting idle.
The same kill-a-watt, same PSU, same ram, same video card, same OCZ V3, same LinX settings, etc but using a different ASUS ROG mobo (the MIVE-Z) and either an i7-2600k or i7-3770k results in (1) higher Gflops (no surprise) and (2) substantially lower power-consumption (by >100W lower).
Now either the CPU is truly burning through 180W of power at stock settings while running LinX or my Crosshair V Formula-Z motherboard is burning through 60W on its own. (seems unlikely)
This brings me back to the CPU.
Now my FX-8350 is burning through power at a rate no one else seems to be able to replicate at stock clockspeeds but it also seems to be turning in a GFlops number that no one else is getting either. My higher power usage brings higher Gflops, stands to reason if performance/W is conserved.
Which leaves us with two questions - why 200W at stock settings, and why do other people's FX-8350 not turn in the same performance? Do these FX-8350 really hit their current throttle running a program like LinX even at stock clocks and volts?
I suppose it is possible, the GPU makers had to implement hardware limits that triggered when OCCT GPU torture tests were activated. Maybe my Crosshair V motherboard is somehow circumventing a set of current restrictors that everyone elses motherboards are leaving in place when LinX launches?