The right wattage for my power supply

corsair have a psu calculator--enter your specs and it will recommend the power you need--you can tell it if you are overclocking the cpu and gpu as well

http://www.corsair.com/learn_n_explore

900W is definitely enough for a system with two 6970s, as such a build would be unlikely to draw more than ~540W at maximum load.
http://www.anandtech.com/show/4061/amds-radeon-hd-6970-...
http://www.legitreviews.com/article/1488/18/
These show a system with an i7-920 and i7-970 (more power hungry than any i5 CPUs I've seen), using ~600W at the wall when running Furmark, which places an unrealistic load on a GPU. Take 10-20% off 600W to find out what their actual system power draw was, hence 540W as a worst case.

900 is more than enough, you could probably boot three cards with that power supply.

why not run a directx 11 benchmark and find out?

unigine heaven benchmark

http://unigine.com/download/

Thanks guys for all your replies. But the went with mcnumpty23 advice and put in the specs and, the minimum I need is a 950 watt. So, I gotta buy a stronger psu.

I think he's wrong but ok http://www.anandtech.com/show/4061/amds-radeon-hd-6970-...

50W won't make any difference whatsoever, if 900W isn't strong enough then 950W wouldn't be strong enough either. Keep your current PSU and save the money.

Corsair are also unlikely to recommend a 900W PSU because they don't sell one.

This bugs me. Of the calculators I've seen they either are run by people who have no idea about PSUs and suggest 500W or 750W PSUs for just about anything. Or they are run by the people who make PSUs. Do you think they want you buying a 400W or 450W if that's all you need? I would love to see a site draw up a PSU calculator, but not involved in PSUs in any other way. Perhaps toms or someone else can make one.

Plus video card manufacturers are famous for over estimating how many watts your system will need. The main reason is all the low quality psu's out in the market. Nvidia/Ati doesn't want anyone to bring a card home and not be able to run it, even on a crappy 500w unit.

I'm pretty sure Anandtech is quite a bit more accurate as they actually did real testing and didn't rely on a software power calculator.

at silvune:

No, they don't have a 900watt it's an antec that I have but like I said, when I put my specs in and they said I need something stronger, they should a 950 watt, a 1000 and a 1200 watt.

They're wrong. The minimum is much lower than 900W which is why you don't need to change from your current PSU.

You seem to have (at least partially) misunderstood what I said. I was saying that if they sold a 900W PSU then they would probably have recommended a 900W PSU, and therefore you wouldn't be convinced that you need to change your PSU.

agree with sportfanboy less than 900W this review power consumption :

http://www.legitreviews.com/article/1488/18/
you have 900W it's great power

All you guys have excellent comments, but still the bottom line is, I've tried both cards in the first pci-e slot and when I put an DX11 game in, no problems no lagging or hesitation from the games. But when both cards are in with xfire mode enabled and I try to play the same games, the lagging and slowness is there. I know it's not the cards or the motherboard so what else can it be. I've purchased a 1200watt in win and when I get it I will see if this solve my problem, whether if it does or not, I will let you guys know.

What I meant to say was they showed a 950, 1000 and 1200 psu's. If the games are lagging at the very beginning when I put the disc in the drive with both cards installed with xfirex enabled but, when I only have one card installed in the first pci-e slot (I tried both) and I insert the same games, no lagging or slowness or nothing. Like I said, there's nothing wrong with the cards or the mobo and that's why I'm going to try the 1200 watt psu. If it still doesn't work I will be sending it back to newegg in a heartbeat.

Sorry, I didn't realise you were actually experiencing problems, I thought you were saying that MSI were saying you'd have those problems if you used your current PSU.

It really seems unlikely to me that your problem is a lack of power, but it is probably a good idea to check with a larger wattage unit anyway.

What motherboard do you have?
What case do you have?
How many games have you tested? It might be possible that the games don't like Crossfire mode.
Very obvious, but I want to double check that you installed all the necessary power plugs.

I have a Asus P7P55 WS SuperComputer mobo
I have the Antec DF-85 Case (the one with the red lights on it)
I've tested Just Cause 2, S.T.A.L.K.E.R. Call of Pripyat (but even with one card in, this game still has issues) and Battlefield: Bad Company 2. Now all three games are DX11 games.

Before, I had a 750 Corsair psu and 2 5850 video cards in crossxfire and I didn't have any issues. Until I bought the two 6970 lightning series cards.
I'm sure I've installed all the power plugs to the video card and to the mobo. Like I said, I'm waiting for a 1200 in win from newegg and I carefully read the comments and reviews on it from people who already bought it and been using it. Like I also said, if it still acting the same, I will return it back to newegg. I will let you know when I get it and see if it works!

Maybe you got one those Antec High Current Gamer 900W Power Supplies that have a problem like Hard OCP encountered during their product review.

http://hardocp.com/article/2011/02/15/antec_high_curren...


AMD's own power supply requirement for a system with two Radeon HD 6970 in 2-way CrossFireX mode is 800 Watts or greater with at least two 75W 6-pin and two 150W 8-pin PCI-E connectors.