Which PSU for crossfire?

c61ll · 31 Aug 2007 at 16:44

Looking for a psu which will run 2 hd2900xt, q6600 overclocked a little, 1 hard drive, 1 dvd writer and 4x1gb pc6400 ram.

was looking at the corsair 620w but just looked on the ati website and says need 750w PSU

needs to fit in a antec p182

Alex UK · 31 Aug 2007 at 16:48

I think the Corsair HX620 would be sufficient. It's been proved that it can handle 2 x 8800GTX's in SLI with an overclocked QX6700.

Failing that, you could buy one of these.

decto · 31 Aug 2007 at 17:03

The Corsair 620w is a good unit.

Although rated at 620w it can divert 600w to the +12v rail which powers the CPU, GPU's etc.

Many cheaper PSU's can only supply 60-70% of their output on the +12v rail. The rest being made up of unused capability on the +3.3v and +5v rails.

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Ps. I have one in a P180

c61ll · 31 Aug 2007 at 17:20

How do these compare to the enermax infinity 650w?

Wingz · 31 Aug 2007 at 18:03

The Corsair only has 1 8Pin PCI-E need for the 2900xt and the Enermax infinity does not have any.

decto · 31 Aug 2007 at 18:26

You're right, The Corsair 2 8pin PCI-E connectors, 1 per card. Two of the pins are detachable for 6pin cards.

You'd need a couple of molex to 6pin cables for the other 6pin sockets on each card.

I haven't seen a PSU in the 600-700w range with 4 PCI connectors.

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LoadsaMoney · 31 Aug 2007 at 23:01

Alex UK said:
I think the Corsair HX620 would be sufficient. It's been proved that it can handle 2 x 8800GTX's in SLI with an overclocked QX6700.

Failing that, you could buy one of these.

2x GTX's in SLi use less power than 2x 2900's in Crossfire, id definately go for 800+.

krisbutler · 31 Aug 2007 at 23:06

ati cards love power get as high a wattage psu as u can thus leaving room for more hdds fans etc etc

krisbutler · 31 Aug 2007 at 23:09

http://www.overclockers.co.uk/showproduct.php?prodid=CA-084-AN&groupid=701&catid=123&subcat=

i have this one which has 2 8pin and 2 6 pin connectors but ill be 100% honest its a little noisy but with 2 graphics carsd running id expect u dont care

c61ll · 1 Sep 2007 at 11:46

so do i need 2x 8 pin connectors for 2x 2900xy cards?

Tempted by the antec quattro if this has 2x 8pin connectors. presume this will fit in the antec p182 case

Delvis · 1 Sep 2007 at 11:55

Correct me if I'm wrong here guys....

But don't you only need the 8 pin connector IF you want to overclock / use the overdrive function on the 2900 etc? Otherwise you can use two 6 pin connectors if I'm not mistaken?

krisbutler · 1 Sep 2007 at 11:57

yes it will fit im not sure on how many connectors 4 crossfire but u get hell of a lot of options with the antec one

willhub · 1 Sep 2007 at 12:28

Delvis said:
Correct me if I'm wrong here guys....

But don't you only need the 8 pin connector IF you want to overclock / use the overdrive function on the 2900 etc? Otherwise you can use two 6 pin connectors if I'm not mistaken?

No, you can either use 1 6pin PCI-E connecter and 1 8pin PCI-E connector OR 2x 6pin PCI-E connectors, if you want to use ATi Overdrive to overclock, you need to use the 8pin PCI-E connector and a 6pin PCI-E connector, but you can use apps like ATi tool and Riviatuner to overclock whilst using 2x 6pin PCI-E connector.

I have a HX520W, as far as I'm aware these or the 620W dont come with a 8pin PCI-E connector, I thought you had to request them and have them shipped from corsair, I know that the 8pin on mine is for motherboard (the one hardwired into the PSU).

Nullvoid · 1 Sep 2007 at 16:09

The 620w Corsair is great, but I would be very wary of trying to run a 2900xt crossfire system using one.