Quote from: Cooldogin on September 26, 2014, 03:29:21 PM

Quote from: bigjme on September 26, 2014, 01:49:07 PM

Quote from: jack80 on September 26, 2014, 01:43:33 PM

Quote from: djm34 on September 26, 2014, 10:14:58 AM

850watt psu for 2 gtx980 and 1 780ti doable ? (with a i7-3770 which doesn't use lots of power)

Yes 165Watt x 2 = 330 watt for 2 980 + 250 watt 780ti = 580 watt .

plus the cpu and the rest of the system, adding to roughly 110W (to be safe), allow for gpu self and manual overclocking, 40w

total = 730w
850w @ 90% eff = 765w (psu efficiency often gets lower the closer to maximum you get)

~spare = 35w

just be careful djm, it may be a good idea to put a kill-a-watt meter on the system if you have one, then add one 980, then another and just see how close they get running some benchmarks each time

Just a FYI on the eff value, that value isn't the output from the PSU into the case, it's how efficient the PSU is at converting AC -> DC and thus it's draw from the wall. Your 850W PSU is rated at 850W and will always output that for the components into the case if needed but it would then pull ~935W from the wall. That being said I always build a ~10% safe value into my builds anyway so I'm not running the PSU at 100% all the time and, as bigjme pointed out, the closer to 100% load the lower the efficiency gets. PSU manufacturers should post their curves online somewhere to let you target the bet place to keep your PSU load wise as well.

yes sorry, eff when i quote it in that instance is usually a 10% safe guard as psu's are known to fail when ran full out. i put eff so none technically minded people understand easier

should have explained that better