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Ok, I have possibly made a minor error. My old card (9500 Pro that was modded to hell and back again) got a little toasted and it worked fine for general usage but would really slowdown in games (I think the memory modules got whacked). So I decided to take the plunge. I recently bought a BFG 6800 GT, I said to myself "Hey I'm going to go big or go home." I popped it in and did a few things and I noticed system stability wasn't great. As in it would reboot randomly. So I reinstalled WinXP and got everything up and going. Same problem. If I do a 3dmark03 test it will reboot part way through.

My thought is that the poor little power supply from the XPC can't keep up with the GT. I tried putting the GT on its own power lead and that didn't really help. I can play some games ok (Dawn of War, older games) just fine but things like Doom 3 don't go well. Big lockups and rebooting.

Now there is one "ahem" minor thing that keeps nagging me in the back of my mind. During my "Computer must be silent at all costs!!!" phase I swapped out the fan in the PSU to a quieter yet higher airflow 40mm fan. I also switched the stock heatsink fan to a Vantec Stealth. Things were good but then this summer the XPC started to get hot. I mean really hot. The metal rails were really warm to the touch and during intense gaming it would turn off and the "I'm too hot" LED would light up. I got angry at the situation so I replaced the Stealth with a Delta EHE. Screw quiet... it's damn cold in there now. So its possible I baked the poor XPC a bit.

Well there you have it. Any ideas? I am trying to limp it along as long as I can until I can do a full new system (2-3 months I hope). Oh and I am not opposed to any modifications to the system no matter how drastic (its sort of a Franken-XPC already). In fact doesn't that make it all the more fun?

sounds like heat problems with the system. Your BIOS should have somewhere the reboot command for system failures. Try turning it off but I highly recommend it. If it is heat problems then you want it to reboot. Not sure how much heat the 6800GTs produce but I just ordered one too !!

Check the BIOS ....usually a lot of people set their bios to ATI's optimals settings. Run your default bios settings and see what happens.

I am assuming you have a blow-hole already in you box?

Ok I disconnected the Shuttle PSU and connected an Antec 550W. It appears to still be having problems.

Sangria7 -- I went through the bios and all the thermal shutdown and other error checking is disabled. Also this cube uses the Nforce 2 chipset. Any other ideas?

I am going to do some driver updating but I am 90% positive I am current with everything.

I just put my GT6800 in today. I ran a test of my own.

1. Run computer with blowhole fan OFF.
2. Run computer with blowhole fan ON.

I have an 80mm hole cut in on the top of my shuttle with a fan running air OUT of the small case.

results

OFF. Computer rebooted 3 times within 10 minutes.
ON. Computer did not reboot at all and is stable thus far.

I noticed it did put out a lot of heat due to the power requiremnents of the card. Your gonna have to cool the computer inner parts some how.

Does that help?

The SN41G2 has the older 200W supply, the newer models have a 240. A friend is running an SN95G5 with a 3500+ and 6800GT with no problem, no special cooling.

Currently I dont have the case on the box so I am pretty sure cooling isn't the problem. I just updated the bios on the box (as it was pretty old) and I am going to do some testing to see if that fixed it. The box is still hooked up using the 550W Antec as well.

I decided to take some voltage readings with MBM5 and either things are quite wrong with the motherboard or the way I have MBM 5 configured. Currently its showing the +5V to be at 3.23V!!! Also the +12V is at 11.13V. This is with the 550W PSU. This might have something to do with the stability problems. Again I am looking into it.

Thanks for the ideas so far!

Well I was finally able to complete a 3dmark03 test. Which is good. I think the BIOS update did the trick. I need to run some more tests but hopefully that was all I needed to do.

FYI my score was 10,096 marks. Is that fairly consistent with other 6800 GT scores?

Thanks again for the help.

10k in 3DMark03 seems pretty normal for a 6800GT...my softmodded 6800 @ 380/860 pulls 9800 or so.

Hey,
I have an SN41G2 aswell, and have been having the same problems. I believe the problem is with the RAM. According to a couple of pages,
here and here there are only certain modules that are compatible with the SN41G2...
Also, you mentioned voltages look too low, I had this aswell, but it had something to do with the temp monitoring setup, voltages were fine.
I'm gonna get some corsair ram soon, hopefully it'll sort the problem. May get a 6800GT too....hope the lil power supply holds up