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Crossfire 4890's - PSU

Fadelity

Fadelity

Fadelity

Associate
Joined
23 Jun 2009
Posts
22
Hi, I recently upgraded my motherboard and memory to accommodate a second Radeon HD 4890 into my gaming rig.
I bought a 600watt Alpine PSU since it seemed the best value but it only has 2x 6pin PCI-e power connectors on. I thought buying 2x 4pin Molex to 6pin PCI-E adapters would be sufficient but when I hooked it all up yesterday it sounded like it was struggling before it decided to power itself off.

Since my graphics cards require 4x 6pin PCI-E's between them, will I HAVE to buy a PSU with those connectors built in or do I have an alternative?
I would have bought one in the first place but I'm on a pretty tight budget and the only PSU's I could find seemed excessive :eek:

Thanks
 
The PSU is one area you really shouldn't skimp on. This powers everything in your PC and, if it goes then it can potentially take other components with it. Quality power supplies will have protection to stop them taking out other things (such as your graphics card, motherboard, CPU), cheap power supplies do not have this protection.

Assuming your PSU is the first one on Google search for Alpine 600W, it cost about £14 from a make I've never heard of, and only supplies a claimed 408W on the 12V rails - the one that actually powers your graphics cards, CPU and most of your other components. This won't be enough for dual 4890s, except possibly at idle.

You will need a good quality 600-750W PSU to power two 4890's. If you get one from a good make (Antec, Corsair, XFX, and others) it will be fine to use molex to PCI-E adapters if you need to, but from a cheap make it definitely will not cope. I always take the view that if the PSU could power 4 PCI-E connectors, they would fit them, and if it can't they won't, but then I like to play it safe with PSUs as I cannot afford to replace components in my PC because the PSU fried them!

This is the minimum PSU I'd recommend for you: http://www.overclockers.co.uk/showproduct.php?prodid=CA-003-XF&groupid=701&catid=123&subcat= assuming you're not running a standard PC with 2 x 4890's (if you're running some dual CPU water-cooled monster then we may need to revise the recommendation)
 
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get a PSU made by seasonic or one of their resellers such as XFX or corsair.
alpine PSUs are basically cheap ones that at best are designed for office PCs that have data stored away from the PC on a network.

as for the power requirement, i would say a good 700W PSU should handle 4890 CF with a good overhead so the PSU is not running at 100% load constantly
 
As others have said you'd need a top of the range 600 W PSU to power CF HD4890s.

The lowest I'd recommend that OCUK stock is the 650 W XFX Confused Stu linked.

The OCZ ZS Series 650W would probably run it, but you'd be close to the limit Max Load +12V 552w and you'd have to use PCI-E adaptors.
 
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