Tri-SLI problem

[Indybird]

Alright, so I'm building one of my friends a gaming computer with three XFX GTX 275s in Tri-Sli on an XFX 790i motherboard. I get the whole computer set up with all three cards in and start it up. The computer starts, but never posts. Also none of the graphics card fans spin up either. I try removing two of the cards, and one of them runs fine. I try adding a second card and that runs fine also. However when I add the third card it doesnt post. I know it has enough power (not like it really matters at boot) as it has a 1000W PSU. I also know that all of the graphics cards are individually fine as I tried every single one by themselves.

Does anyone know what could be going wrong here?

Thanks,
Indybird

[Collinstheclown]

Perhaps a BIOS update?




-CollinstheClown

[Luke122]

BIOS gets my vote as well.

You said it works with one or two cards.. have you tried testing them each individually?

[Indybird]

BIOS gets my vote as well.

You said it works with one or two cards.. have you tried testing them each individually?

Yeah each one works individually, I'm going to try the BIOS update when I go over there. Thanks for the help.

-Indybird

[Luke122]

I am getting rusty at this, but I seem to recall seeing specialized SLI memory in the past.. could this be the case here?

[Indybird]

I am getting rusty at this, but I seem to recall seeing specialized SLI memory in the past.. could this be the case here?

I never understood the purpose of SLI specialized memory; do why it was SLI specialized?

-Indybird

[Crazy Buddhist]

If you have SLI bridges are you sure you have them configured correctly and BIOS settings too?

Always worth updating the BIOS but may not solve your problem...

CrazyB

[Indybird]

Alright we solved it. The power supply (Xigmatek 1000W Modular) only had two +12V Rails on the PCI-Express connectors. That would've been fine except there were three connectors on each rail which means one graphics card is powered by two different rails. Well apparently that doesn't work too well.

So we hooked up the card via some molex connectors onto the 3rd +12V rail (which has a disk drive on it ) and it runs fine now.

-Indybird

[Luke122]

Excellent! Definitely an unusual problem!

[nevermind1534]

I'll have to keep that in mind, in case I ever do something crazy like that.

I never understood the purpose of SLI specialized memory; do why it was SLI specialized?

I think what it allows, is for the memory to run at a different (faster) speed than the FSB.

I sell craploads of the OCZ SLI 4GB kits on ebay.