Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I purchased a second video card for my machine so that I could setup a 3 monitor system but I am experiencing an issue where the machine will constantly reboot. I see the post screen for a second or two and then the machine reboots. If I remove either of the cards, leaving the other in the machine, the video output is fine and the box boots into Windows as expected.

Both cards are NVidia. One is PCI-E and the other is PCI. I have tried switching between the primary cards in BIOS (either PCE or PCI-E) but that doesn't seem to help. Are there any other issues that I should be aware of that may cause this? Any advice on how to debug the issue?

EDIT: Way off on the video card before. It was actually the crappy one that came with the case. It is 500 watt with 1x 12v rail at 22A. I tried a 700 watt with 3x rails at 18A. It did the same thing.

  • Motherboard: Biostar NF4-A9A
  • PCI-E Video Card: NVidia GeForce 7600GS DDR
  • PCI Video Card: NVidia GeForce 6200 DDR2

Just noticed the difference in DDR and DDR2. Is this the issue?


There are 2x 1GB sticks of memory in there. If I take 1 out the machine boots fine. I just bought 2 more sticks along with for a total of 4. If I try any one of the sticks the same thing happens. As soon as I put a second stick in the machine doesn't boot.

share|improve this question

migrated from Apr 4 '11 at 23:59

This question came from our site for system and network administrators.

Seems like a case of mismatched RAM timings. – Sathya Apr 5 '11 at 6:42

Probably a power supply issue. Graphics cards pull a lot of power.

I had one of the first AMD machines that the local shop had sold. It booted fine in Linux, but couldn't boot with Windows. Turns out that they'd undersized the power supply, and Linux starts the graphics card and the sound card at different times, but Windows starts them both at the same time, and it didn't have enough power for the initial power spike on both of them at the same time. We got a better power supply and it was fine. And the issue wasn't the total watts of the power supply, it was how much it put in the +5v rail versus the +12v rail or something like that.

share|improve this answer
I was way off on the power supply spec before but I've updated the post. I tried a different power supply and it had the same effect. – Adam Driscoll Apr 5 '11 at 1:10

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .