After replacing my motherboard and power supply, the system posts then reboots u

I've recently been given a computer. It's a great machine, but it had a nasty habit of randomly rebooting every 3-24 hours. After extensive troubleshooting, I narrowed the problem down to either the motherboard or the power supply. I contacted the manufacturer (@XI) and they sent a replacement for each.

The motherboard is the same model and revision of the motherboard replaced (EVGA nForce 680i revision A1), while the power supply is a different brand.

After replacing both items (essentially a full system rebuild), the computer will not load Windows 7. It posts fine, then attempts to load Windows and reboots. It will not run in safe mode, and it will not boot an installation DVD. It appears to load drivers and then crap out.

I've done everything I know to do; I've updated the motherboard's BIOS to the most recent version (incidentally, the same BIOS version the previous motherboard was on), I've cleared CMOS, I've loaded the default BIOS. I do not have another version of Windows handy to try, so I haven't been able to test if this is a Windows 7 specific issue.

Does anyone have any ideas? I've been working on this all night and am a bit frustrated to say the least.
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More about after replacing motherboard power supply system posts reboots
  1. Update: I found my old Vista disc, and it does the same thing. Posts, attempts to load off the disk, gets as far s "Starting Windows" and craps out.
  2. Second update: I've tested the memory and expansion cards. I replaced the power supply with the older model. So far nothing has made any change.
  3. OK, first, have you formatted the hard drive and reinstalling Windows? That would eliminate any software issues if that's what the problem is. Or can you not even get far enough to reinstall? (which would indicate a likely hardware issue)

    My next question is, what kind of RAM are you using, and what voltage is it supposed to take? A system can freeze or reboot if stressed under too low a voltage.

    So what could be happening is that the board is defaulting to supply too little voltage to the RAM, and as soon as a program too hefty for it comes along -- POP! -- it crashes out. So it does OK for the startup routines, then Windows 7 proves too much for it. A CMOS clear wouldn't help, because you'd be resetting to the same default voltage, which is too low to begin with.

    So try looking for your memory's voltage specs, look up the board's default voltage specs, and if they don't match, there's a possible suspect. The fix would be to go into the BIOS and adjust the memory voltage to whatever is needed.

    As far as I know, this could also be the same issue with CPU voltage, although that's less common. RAM voltages are all over the place and often need adjustment. No guarantees, but I hope that's what's doing it.
  4. I'm unable to get as far as a format/reinstall; that was on my check list.

    I'll check the RAM voltages. This is far and above the most powerful computer I've ever worked on... Is setting RAM voltages a common activity on enthusiast machines?
  5. That doesn't appear to be the problem. The memory is specced at 1.8-1.9v, and it's set at 1.85v. I'm starting to fear I've been given a bad motherboard.
  6. Setting RAM voltage is a VERY common issue not just on enthusiast machines but any homebuilt system. It seems to be the last thing on memory manufacturers' minds, so with a lot of higher-performance RAM, there's a good chance you'll be adjusting something yourself. A lot of motherboards are good with handling that, but certain ones will give you headaches for no good reason.

    In your specific situation ... well, it doesn't look like the memory was the problem. That's a bad sign. My next guess would've been the power supply not being able to provide enough juice under any kind of load, but it looks like that's been ruled out as well. Motherboard would be my next guess -- I'd give it a VERY careful once-over for little nicks or scratches, especially around the CPU, card slots, or anywhere else someone would use a screwdriver. Maybe even the back if it was set into the case too roughly.

    But that's just a guess at this point. I hope it turns out to be something else.
  7. I've replpaced the motherboard with the original problem board, and it's at least booting up. I imagine that it will still have the random rebooting issue, but at least I can get into it now.
  8. Now that's odd. Wonder if the second motherboard was just a bad board, then?

    Don't want to harp on the RAM issues, but one last question: Are you using two sticks or four? If you have all four slots filled, one more quirk is that sometimes that makes voltage requirements even higher than manufacturer specs, so that could be an issue. If so, try it with just one stick first and see what happens.

    The other thing that comes to mind is that maybe it's a software issue, like not all of the board's drivers are up to date for Windows 7. You said you updated the BIOS, but did you also update things like chipset software, LAN drivers, and so on? I've read a few things about that board having driver issues with Windows 7, although most seem to involve the ethernet port. At this point, I'm just throwing ideas out there.
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