Random Reboots and freezes

Hi there,

4.5 years ago I bought my current system:
- Gigabyte GA-P35-DS4, Intel P35
- Core 2 duo E6850
- 2x1gb crucial ballistix CL4
- Enermax Liberty ELT500AWT PSU

A few weeks ago the graphics card (an nvidia 8800 GTS OC) went bust, so I had to decide to either buy a completely new set of components or just replace the graphics card. I don't game *that* much so I decided to just go for an nvidia GTX-560 TI which is just about appropriate not to be bottlenecked by the CPU, at least at 1920x1200.

In any case, The PC now randomly crashes and freezes in any of the following manners:

- Starts and hangs at POST (e.g. after counting memory or after 'verifying DMA pool data)
- Starts and runs fine, I even played Assassins Creed 3 and Crysis 2 for a short while without a problem, ran windows update and rebooted fine. But then...
- It crashes at any random point, e.g. during POST, boot up, while in Windows or Linux at any rate between a few seconds and several minutes
- From a cold start, nothing happens, black screen. Hitting the reset button doesn't do anything
- From a cold start, black screen but the PSU is making that 'tick' noise every second as if I were pressing the reset button all the time
- The reboots are either immediate (as if pressing reset) or off/on with a powered-off pause of 2 seconds.

Unfortunately I don't have any replacement HW I could test in it, but two weeks ago when the 8800 went bust, I had another GPU (a GT-240) in it and everything ran just fine. The PSU is strong enough for the system and all the wires are plugged in correctly. I tried resetting the BIOS.

It's seriously irritating that the reboots happen at any point and that sometimes, the Box runs fine for 20 minutes even when playing games and stressing both CPU and GPU.

Any ideas how I could figure out which component is the problem other than sourcing drop-in replacements? I don't have a volt meter but I could buy one, I wanted one for a long time.

5 answers Last reply
More about random reboots freezes
  1. Sounds like it's a problem with your PSU. One of the rails probably cannot supply enough current.

    That card can sink up to ~ 320W at full load ( 2 6 pin connectors! It need's its juice). That + everything else in your system will put stress on the PSU you have.
  2. I'll try sourcing a PSU, although nvidia officially says 500W is enough and the TDP of the GTX-560 TI is 170W. It's also odd that the reboots are this random and not consistent when playing games.
  3. I quickly read a review and misread one of the power measurements, so you are correct that the 560 under max load will use around 170W.

    If they truly are random (don't seem to increase in frequency when the PSU is hot for example), then you might also be looking at a bad GPU. I would also check that it's sitting in the PCIx slot correctly and that the two modular cables you have powering it are properly connected.

    A 500W PSU should be fine but a PSU can degrade quite substantially over time. If any 1 rail is being severely taxed (even if you are running under 500W) than components in you system might not be getting enough power.
  4. I wouldn't discount the PSU as the problem just yet. Keep in mind that the PSU is over four years old and may not be performing up to the same specs it did when it was new due to aging. Also, have you opened up the PSU and made sure that you don't have excessive dust built up inside. That could cause overheating and eventually failure of the PSU. I seriously doubt that it is under warranty by now so you should be able to open it up without that concern.

    Also, keep in mind that the GT-560 TI is still using quite a bit more power than either of the previous two cards you mentioned. The GT-240 uses 120W (and the 8800 likely uses significantly less) vs the GTX-560 TI at 170W. That extra 50W translates to over 4 amps. I would seriously look into gettting a slightly larger PSU. BTW How many other devices do you have hooked up that could be drawing more power such as harddrives (multiple?), USB devices etc.
  5. Thanks for all the input, but I think I've found the culprit. Most unexpected fault in history:

    Faulty reset switch!

    I disassembled the whole machine, layed out the components on the table and started with just psu, mobo, ram and cpu. The system was stable and I worked my way back up putting everything back in the case, including all the disk drives and fans, everything.

    Then I reconnected the front switches and the reboots were back that instant!

    Somestimes it really isn't what you expect, but this explains why the reboots were truely random, it didn't have anything to do with any of the components...
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