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How much PSU do I really need?

T

Topaz

Limp Gawd
Joined
Dec 27, 2010
Messages
253
Greetings all.

For a while now I've been planning to put together a rig later this year. It'll be my first time building myself. I'm a little worried, but I've been doing my research for months, so I feel like it should go fine on the whole. However, I've been uncertain as to just how powerful a power supply I need.

I'll probably wait to see X79 before taking the plunge, but my current plans are as follows:

Case: NZXT Phantom (fans 3x200, 1x140, 3x120)
Mobo: ASUS P8Z68-V PRO
CPU: i7 2600K
Cooler: Corsair H100 (just hope it fits the case...)
RAM: 4x2gb 1600
SSD: OCZ Vertex 3 120gb
HD: Caviar Black 1TB 7200rpm
GPUs: 2x 6970 CrossFire

For some time I had been looking at the Corsair AX1200, both because it had been so well-spoken of and because I knew that would definitely be enough, but having looked at the power draws of dual 6970s, am I wrong in thinking that's too much money to be spending? What's the best wattage range I should be looking at? Would 850 be enough, or would it be safer to go with 1000?
 
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Have a look here, it's precise and rather easy to understand:)

Clean and simple answer: 800/850W will be plenty
 
850w will be more than enough for just 2x6970's. I'm running a 6990 and thinking about adding another 6970 on a Corsair AX850.
 
Thanks for the responses, and wow, thanks for that link, really informative. I never would've thought a 6990 could run off just 550W...
 
A 6990 not overclocked will run just fine with a 550 watt. Overclocked, you want to bump that up to ~750 watt. And since a 6990 is essentially two 6970's, two 6970's will run just fine off a 750 watt. I have two overclocked and unlocked 6950's (essentially 6970's) running just fine off my Seasonic M12D 750 watt.
 
A good quality 850w PSU will be more than adequate. You could honestly run that whole rig on a corsair 650w PSU and you'd be basically maxing it out but it would provide enough power at stock gpu clocks and a OC I7 2600k. I've kill-a-watt tested 3 6950's flashed to 6970's on a I7 930 stock and it took 680 watts input so this means the output voltage of the corsair TX650 was under 650 watts which is fine. This was done on a bitcoin setup so the CPU wasn't really being utilized but all 3 gpu's were at 99%.

I'd go for a a good quality 850w psu.
 
Yeah, already updated my newegg wishlist with the Corsair AX850. Thanks again for all the excellent responses. :)
 
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