Hi,

Ill start off with my spec:

CPU - Intel Core 2 Quad 2.66 GHz Q6700
Graphics Card - 2 x 9800 GX2 1G
Ram - 4 x Ballistix 240-pin DIMM 1G DDR3-2000MHz
PSU - Enermax 1000W
Motherboard - nForce 790i Ultra SLI

Now for the problem:

I hooked everything up and turned it on with fingers crossed. It turned on but then forgot to put a monitor to the system so i turned it off and put the monitor into the system. I then rebooted the computer which it started up but i had no display and red lights on the graphic cards. It keep coming up with two codes 7F and P5. I decided to replace the new GX2's and add a old graphics card into the motherboard and it loaded fine without any problems. I hooked them both back up, and nothing absolutely nothing. I even tried it with one graphics card and still nothing. I have set the BIOS to do PCI-E instead of the default PCI.

The P5 code is when the screen has display, it says use #1 PCIE slot and says it detects a card in #2 or #3 PCIE slot although theres a card in #1 PCIE slot. Could it be a dodgy PCIE slot?

The 7F code is something to do with use intervention (i never got the full story about the 7F as id id not understand it atal)

Also, when i hook up the GX2's i cannot get into the BIOS screen, the only way i can get into the BIOS screen is to place a old graphics card into the #2 PCIE slot and boot that way.

Would resetting CMOS help? and how do i reset it?

Answers would be nice = confusing topic this one.

If these are brand new cards, and neither work individually in either slot (please confirm this) that means that either they cards are bad or the motherboard has something wrong with it. Considering that an older card is working I would lean towards the cards being bad. Another possibility would be an underpowered PSU but I doubt that is your problem. I hope that a 1 kilowatt PSU would provide enough juice. If you can go further and test the cards on another desktop that would be great. Either way if they are under warranty I would RMA them. This would be a different story if they worked individually. You can try to go into the BIOS and rest all configurations to the manufacturer's defaults if you want. What I find interesting is that both could be bad. Either you got a few from a bad batch or trying to run them together killed them which I would find just as weird as your problem.

Next time just to be sure when you install the cards I would install each individually to make sure that they are working before you put them together that way if you do have a problem you can narrow the possibilities down. Good luck.

Unfortunately i have already fixed the problem with the cards, i wired them wrong and needed to change setting on BIOS. I am glad to say that i have installed vista successfully and even better the cards are running nicely in quad sli. Thanks for trying to help me though

Thats good news. I never done an SLI but I know that with computers you have to watch the wiring or, at the very least, it won't work and might even mess up something. You also need to configure this correctly.

Why is it unfortunate that you fixed the problem?

In that sense, yes. Well, i didnt really wire them wrong, i just missed a wire so it wasnt getting enough power to them.