I apologize for the wall of text (I hope) you are about to read, but I feel all these informations are relevant.
Feel free to make any suggestions for a solution, or to ask me any uncovered detail I might have missed.
About two months ago, my GTX275 video card displayed green artifacts during a game and hard froze my system. I restarted the pc, continued my game, then about 5 minutes later it happened again, only this time it was impossible to boot after restart.
When turning on the pc, all fans and LEDs were working as usual, including the one on the video card, but there was no display on my monitor and the computer wouldn't boot at all (no short beep, no nothing, just a constant black screen).
I had another video card around, an 8400 GS, so I tried replacing the GTX275 with that. The system worked fine with the second card, but not with the first one. Naturally, I thought the GTX was broken, so took it to the service (warranty), to be repaired.
While GTX was being in service (took about 1-2 weeks), I've been using the 8400GS on my system. During this period, my computer would hard freeze as often as once every 15 minutes. Happened most during any game, happened less while doing a random thing, such as watching a youtube video, and happened least when my pc was idle (for example when I was not using it, or I was just reading a forum).
I have tried the following:
-installing a previous version of the video driver, didn't help
-reinstalling the os + all drivers and programs, didn't help
-scanning my pc for viruses/malware, found nothing
-running memtest86 for hours (5 passes), got no errors
-running MHDD for hours (1 pass), got no errors
-running all tests in OCCT for about 2 hours each, got no errors
-resetting my bios to Optimized Defaults, didn't help
-resetting my bios to Fail Safe Defaults, didn't help
Note: the 8400GS is the card I was using in the secondary pc. It has NEVER froze my system prior or after this event on THAT computer.
After I was called to pick up my GTX275, they said they found nothing wrong with it at all and it's in perfectly working condition, so they just gave it back to me (while also required to pay a fee for unjustified solicitation of service). Obviously, I was confused. I went home, tried it, and the pc turned on as by magic. I am not sure/forgot if the hard freezes suddenly or gradually stopped after that, but they did stop.
II. Present day problem
3 days ago, my GTX275 video card displayed green artifacts during a game and hard froze my system. I restarted the pc, only it was impossible to boot after restart. When turning on the pc, all fans and LEDs were working as usual, including the one on the video card, but there was no display on my monitor and the computer wouldn't boot at all (no short beep, no nothing, just a constant black screen).
I have replaced it with the 8400 GS. The system worked fine with the second card, but not with the first one. Sounds familiar?
You guessed it: my system started having hard freezes again, although not that often as last time (yet).
Today I have completely disassembled my pc and gradually rebuilt it to test each component and each slot. Everything went fine until the GTX, of course. I carefully inspected every component for any kind of visible damage and found none.
To make things worse, my warranty for it expired 2 weeks ago, but I have a believe that it would have happened the same as last time ("unjustified solicitation").
III. System configuration
MB: Gygabyte GA-MA790XT-UD4P
CPU: AMD Phenom II X3 720 2.8GHz
HDD: Western Digital Black Caviar 1TB WD1001FALS
Ram: Corsair TWIN3X4096-1600C9DHX 2x2GB DDR3 1600MHz
GPU: BFG GeForce GTX 275 896Mb DDR3
PSU: 550W Rasurbo SilentPower DLP 55.1
Audio: USB (external) Hercules Muse Pocket LT 5.1
OS: Windows 7 32b
All components are 2 years old.
IV. Personal conclusion
I have a strong feeling that the GTX 275 is not to blame for everything, as serious problems (hard freezes) exist even when replaced by the 8400 GS.
I have no idea WHAT component or setting in my system is causing all this.
Please help me or guide me to someone who can help.
The GTX 275 requires 2x 6 pin cables to be powered.
My secondary PC is way older and has a weak PSU. It has no 6 pin cables at all.
I did try the GTX on it, while powering the card with my main PSU (while the rest of the system was powered by the secondary one), but it seemed to act the same: all fans powering on, no booting, no beep, no display.
However, I did not ever test the GTX on that system while it was still working(?), so I can't confirm that it worked before and now it doesn't.
As for the memory, I have tried each stick in each slot separately and are working as normal. I cannot confirm that I get hard freezes with a single stick because I cannot reproduce them; they happen randomly, way less often that were happening 2 months ago. Also, as I said, I ran memtest on them for 5 passes and got no errors, also the memory tests from OCCT.
I ran memtest with both sticks of ram inserted.
My bios settings for ram are at the moment manually set to 9-9-9-24 1.8V 1600MHz, which exactly matches the specifications on the ram.
I have also tried setting all on Auto, but nothing changes as well as the no booting with the GTX or freezes are concerned.
I have been monitoring the temperatures and none of them seem unusual. At maximum load, CPU temp goes to about 45 degrees (celsius), HDD about the same, motherboard PCB the same, GTX card goes up to 80+ degrees during some high system requirements games like Witcher 2, but typically stays at 60-70 degrees during most games. These are the MAX temperature each component reached while monitored.
I cannot reproduce freezes to check if it's network related because, as said, they happen less often now than before.
My system isn't and wasn't ever overclocked, no component was ever set above their system specifications.
Quick recap of the timeline of events
1. PC worked flawlessly for more than 1,5 years.
2. the GTX suddenly stopped working and was sent to warranty
3. during this time I've been using the GS, got often hard freezes
4. my GTX was returned saying it was fine and no malfunction was detected
5. installed the GTX, it was working indeed, all the hard freezes were gone too
6. two months later, GTX crashed again and wouldn't start
7. replaced it with the GS, hard freezes started again but way less often
Also, some time (months?) before first GTX crash, I replaced my PSU twice. First one it went down with a boom (literally), the second one started to smell very strong, so I got it replaced before waiting for a boom. The current PSU has never displayed any problems.
Both my PSUs happened to fail during the same game (Gothic 4), so I never tried it again on my 3rd PSU.
try mem test with one stick at a time, using the same slot.
You seem to have an issue that is rarely achieved and when it is it either hard freezes your GS or shuts down your GTX to a point where it fails to recover.
Are you running your pc off surge protector? UPS?
I am inclined to think that you might have a low quality PSU that might be getting overloaded which leads to problems. Can you check the PSU temp under load? (I know there's no sensors in there, but just feel how hot the air coming out of it is) Preferably the questionable Gothic 4 or try with Witcher 2. Out of the PSU's that failed previously, what was the raiting on them? also 550W? Maybe 550W isn't enough for your system?
Now that you've been using your GS again for a while, have you tried putting GTX back in again? Do you remember under which conditions it crashed?
I've tried memtest with each stick, 2 passes, no errors.
I have an UPS which I don't use it because it's 600VA, not enough to keep my system running in 3D applications.
My electrical sockets are grounded though, if it counts for something. I have also tried plugging in the pc to another socket from another electrical system and it doesn't act different.
My PSU temperature doesn't seem off the charts. Nothing wrong there as far as I can tell.
The past PSUs were 535W and 550W. Current one is 550W. I don't think a pc would work while on heavy use for more than 1 year with a PSU that is doesn't provide enough power, so I guess it's safe to exclude this variant. Also, none of them were low-cost.
I can't test neither Witcher 2 nor Gothic 4 because they do not work on 8600GS. I wouldn't test Gothic 4 anyway, wouldn't want my 3rd PSU burned, especially since it's now off warranty.
I have tried today my GTX again (after 6-7 days of not working) and it still doesn't work.
Time doesn't fix things...