Power needed for 2x HD5870

[blair]

How much watts do I need to run 2 HD 5870 in crossfire;

 

[kilobravo]

750w is enough.But for oc`ing both gpu and cpu 850w is safe bet.

 

[blair]

ive got a 750 the gpu's wont be OC much the CPU will be my target is 4Ghz again when new MB gets here was wondering as i have 1 hd5870 atm and when its a little outdated wondered if i could chuck another 5870 in there to boost the performance.

 

[kilobravo]

There should be a nice boost,and 750w is enough.

What psu do you have?

 

[KING_OF_SAND]

OVER 9000!

but really i would just get a 1000w by a reputable company, it will last you a while.

 

[S_I_N]

well the 5870's spec says 500watt for single card and 600watt for dual cards but as said depends on oc and also depends on what else is in the system drawing power. For instance if it was a single hdd, optical cpu and dual gpu's then 750 would IMHO be bare minimum for oc on cpu only. Think of it this way each 6pin pci-e power cable is 75watts they have 2 so thats 150watts there alone. Now in addition the pci-e slot also gives the card 75 watts now were up to 225watts double that and were talking 450watts from a 750watt psu now I dont have the exact numbers for cpu's hdds, optical drive mother board power and case fans and what not say thats another 100-150watts (guestimation) now ur at 550-600watts so IMHO it will be running at or around 75-85% all the time (math is most likely off) but just for example so in reality I would say you'd be safer with a 850-1000watt psu so its not running full boar when loaded. Again these numbers are not exact and I am talking full load scenario The only real way to determine is to get one of those power draw meters and see what ur actually puling at full load.

Main reason I say alot of this is because I am running 2 ssd 4 hdds and an optical drive with 6case fans on a Corsair 750watt psu and I have noticed I cant reach my old oc as before and I am pretty sure its due to all the extra drives I have running atm. so basically I am saying there more to weigh in than just 2 gpu's