View Full Version : Problem: Is it the 8800GTX, or is the PSU

04-21-07, 11:13 PM
Ok, I've been getting back into Oblivion, now that SI is out and SLI works great again under the 158 drivers. However, I'm having a problem when in a complex scene, my computer will instantly power off. No warning, no CTD, no BSOD, nothing, just off. This only happens with Oblivion, and only with SLI, both of which together will get my total system draw on my UPS (monitor + computer) above 500w (I've also tested with the computer plugged directly into the wall). I'm thinking this is a problem with my power supply, but I'm wondering if this could also be an issue with my second (older, first shipping batch) 8800GTX; I accidentally scraped my old sound card over the back of the GTX when I was replacing it a couple of weeks ago. The GTX doesn't appear damaged, and the problem's behavior is more in line with a power supply fault, but I want a second opinion.

Edit: On second thought, SLI always worked fine under XP, without issue, and this PSU only has one 12v rail, so it should crap out no matter what I do, if it was defective. Maybe I did cause a short on the back of the GTX...

04-21-07, 11:51 PM
I don't think your PSU has enough juice for 8800 GTX SLI.

04-22-07, 12:06 AM
It's definitely your PSU. I read about people having similar issues with 7800 GTX 512MB SLI and Obvilion and once they'd upgraded their PSU, problem solved.

04-22-07, 08:42 AM
It's a 1000w PSU! It's got 72 amps on the 12v, and 24 amps on the 3.3v. It damn well better have enough juice. That said, after using the suspect 8800 for a short time without problem (in a known problem area), it looks like the PSU has developed a fault.

04-22-07, 09:29 AM
Add another PSU to make sure. :thumbup:


04-22-07, 01:21 PM
i had this problem when i had my 7800GTX in SLI, instant shutdown in some games, even my PSU was a 680W that should have been enough for 780GTXSLI.. But i replaced my PSU to a 750W and the problem went away..it seems that my PSU got defective or whatever.. Maybe it is ur problem too.. Can you borrow a PSU from a friend and test ur setup ?

04-22-07, 01:49 PM
If your worried about the 8800GTX having a short or damage do to the scrape you caused with your sound card, why not plug the one 8800GTX in and see if it shuts down your computer? If the 8800GTX is defective it won't matter if it's in SLI or Single, at least I wouldn't think so. Otherwise, I'm going to have to agree with everyone else, it really sounds like you PSU is underpowered. What's the AMP's on your 12V Rail? That could make a huge difference.

04-22-07, 01:57 PM
I used the second 8800 as the primary card, with the known good card out of the system. It ran fine, and I couldn't replicate the problem. As soon as I plugged the good in as the second card and reenabled SLI, the computer shutdown almost instantly in my test game.

Right I've got my old 750 watt PSU hooked in as a secondary power PSU (feeding the 24-pin ATX and the second GPU, while the 1kw feeds the 8-pin motherboard connector, first GPU, fans, DVDs and HDs). Time to see what happens... This thing looks like Frankenstein's monster.

Edit: Ok, with the second power supply added in, everything runs fine. Looks like its RMA time.

04-23-07, 08:58 AM
I see you have your Core 2 Duo overclocked .In your signature you have the CPU core and NB increased and the rest on auto,does this mean you have your CPU FSB increased also because my at auto runs at 1.2v. With my running the CPU FSB at 1.2v causes reboots and game freeze and blue screens ,I run my CPU Core at 1.3v but I need my CPU FSB set to 1.4v for everthing to be stable .

04-23-07, 09:36 PM
This has started to happen recently to me as well. I was able to lessen the frequency of the "turn off's" by unplugging 2 HDD's. So im pretty sure in my case its just my PSU getting right on limit.

Its odd tho can play hours of games then bam.. off.. then again for hours and its fine.
Pretty sure its PSU tho.