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Single rail PSU solves RD480 Crossfire problems

Xtremesystems, Sampsa, ATI and support guys confirms it
Mon Feb 27 2006, 21:32
WE have a solution for problems that we have had with A8R-MVP motherboard and two graphic cards. You can check the original post here. We spoke with many people today and they all indicate that it has to be the power problem.

ATI key motherboard designer John Bruno told us that a single rail PSU is better than a multi rail PSU. He reported that ATI had some issues with multi rail PSUs while all of the single rail 500 W + PSUs were running fine. It turns out that both OCZ Power stream 600 W PSU and Akasa 650W PSU are using more than one power rails.

One of the readers an administrator of a motherboard company forum recommended ENERMAX EG651P-VE FM(24P) PSU with 36A and a single12 V rail. Our colleagues at Bit tech managed to test dozen X1900 cards including Crossfire with a single rail 520W OCZ PSU. You can check the article here.

We got a nice link where one of the top overclocker, our good friend Sampsa had the same problem with 600W multi rail PSU and A8R-MVP board and two X1900 cards in Crossfire. He solved its troubles by switching to a single rail 560W PSU. You can check the post here.

This specific problem reminded us on the same problem that we had with two Geforce 7800 GTX 512 cards. Those two cards in SLI were crushing the machine while two 7800 GTX 256 MB cards worked flawlessly. You can check it out here and we have been working for two weeks with Nvidia to solve the problem but failed to make it work. Someone simply could suggest that we should try single rail PSU 500+ W and everything should work. SLI works with two 7800 GTX 512 after all.

Hurray, now we know that Nvidia and ATI should warm people that they need single rail PSU not just any 600 W PSU. That really makes the difference. We are speechless why no one warned the users about this issue.

Despite we have two 600+ W PSU we are back at the spot where we need to get a new PSU for the lab to test those power hungry rigs. Asus A8R-32 MVP Deluxe board powered with RD580 chipset can even work with multi rail OCZ 600 W or Akasa 650W PSU as we guess it is distributing the power better than the previous one. A mystery solved, but beware if you are buying top motherboard SLI or Crossfire and you want to plug two power greedy cards inside. You need a lot of quality single rail power, not just any power.

Thanks for all the mails with suggestions. µ


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