Power usage for 2x GTX 780 in SLI?

Globber · Mar 1, 2014

Thanks in advance for answers. I recently picked up an EVGA Classified GTX 780 and plan on going from 2 to 4 monitors. When I do so I would like to SLI a second 780 card. I am currently running a KingWin 80+ Bronze 1000 watt PSU that is almost new. All cabling is interchangeably modular and it lists it lists 83 amps on the 12 volt rail. I have used various wattage "calculators" and seem to get different answers from each of them. I am not that familiar with SLI power consumption and want to know if this PSU will handle these cards in SLI?

I also have 3 SSD and 3 HDD and 12 case fans. Not sure how much closer that will push me.
Thanks!

Bad_Kitty13 · Mar 1, 2014

each 780 is 250w cards you divide that by 12 the 500w by 12=41.66a
most chipset tdps are around 24-36w divide by 12=that is 2-3a
you didnt list your processor but i will say that even if it is a 220w 9590 vishera(the highest tdp processor)divide by 12=18.3a
then throw on 1a for your cpu fan and 5a for an overclock you may have that equals 68.96a
you said your 12v rail was rated for 83a and general rule of thumb you always want to leave 5a headroom so that brings your 12v rail down to 78a
so if you have 78a on your 12v rail and you are running (worst case scenario) 68.96a. you have more than enough room

Bad_Kitty13 · Mar 1, 2014

you should always always always do the amperage off the 12v rail some cheaper power supplies say they are rated for ---w when they have 2 12v rails where then you have to worry about which rail you are attaching things too psu calculators are good to get you in the ballpark but always do your 12v rail amperage. you dont do that and it could fry the whole system or kill the power supply if it has weak enough components. and your 12v rail is 83a which means it is rated for 996w just if your curious the other 100w in your psu are other rails like a 3.3v for molex connectors a 5v for sata connectors just depends on what it has.

Globber · Mar 1, 2014

Yes i have a 3.3v and a 5v each at 24 amps, and a 5vsb at 3 amps. I am running an FX8350.

Bad_Kitty13 · Mar 1, 2014

your rated performance should be fine.
that being said kingwin performance is all over the place they have powersupplys in tier 1 tier 3 and tier 5
http://www.eggxpert.com/forums/thread/323050.aspx
take some time and see where your psu is on this list if it is not one of the listed kingwin models then it is a tier 5 and may not give you the performance you are looking for. if your psu is in tier 1 2 2b 0r 3 you should be fine. if you have anymore questions just ask

Globber · Mar 1, 2014

Thanks Bad_Kitty, your input has been very helpful. My specific PSU is listed on that list under tier 3, the only KingWin listed under tier 3 is mine. My old ThermalTake 650 gave me stability problems, as soon as I swapped to this 1000 watt PSU my problems and freezes stopped immediately. I think based off of your input and some other research that I should be fine. Let me know what you think. Thanks!

Bad_Kitty13 · Mar 1, 2014

Globber :

you most likely will be. even if it is not running to spec it shouldnt be be more of 5-10a decrease on your 12v rail. one good way to tell is to see if your voltages are spiking on your system now. and i dont like thermaltake either. best manufacturers are xfx evga seasonic as far as all psu components being of quality.

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