Power related questions

[grue]

How much power does a standard ATX motheboard consume?
If i'm mining for a long time, how much % of a PSU's rated capacity should i use? (it's an antec earthwatts, by the way)

thanks 

[diabinc141]

Need way more info. What motherboard, CPU, GPU, and PSU, etc do you have?

[rjk]

Be sure to consider the fact that the PCIe slots also consume power that is pulled via the mobo itself. The spec allows up to 75 watts per slot, but most cards pull between 20 and 60 watts each.

[grue]

2x 5850 (150 W each)
AMD phenom quad core ~100 W TDP
750 W antec earthwatts, the one with 4 rails

I was considering to add a third GPU, but i was not certain if my power supply could handle it. 150*3+100 is already 550W, and that's just the GPU+CPU, not including other accessories.

[DeathAndTaxes]

2x 5850 (150 W each)
AMD phenom quad core ~100 W TDP
750 W antec earthwatts, the one with 4 rails

I was considering to add a third GPU, but i was not certain if my power supply could handle it. 150*3+100 is already 550W, and that's just the GPU+CPU, not including other accessories.

With underclocked ram it is unlikely your 5850s are pulling 150W and while mining your phenom is certainly not pulling 100W.  Best thing is to get a kill-a-watt and measure.  I know that sounds like a copout but there are so many variables in play anything else is a rough guestimate at best.

[diabinc141]

I don't know much about that PSU but I like to not load PSUs up to much unless they are really high quality (for example Seasonic). Also single rail designs are much better however multiple rail designs can be managed. Just make sure you don't have the CPU bug that makes it run 100% while mining and you should be able to run 3 cards assuming you cut down on accessories. In it's current configuration (with DVD drive, hard drive, fans, 100 watt CPU, etc) you'd be cutting it too close for comfort.