Completely random computer restarts (crashes?) on any OS

Question

My computer sometimes suddenly restarts. This issue has always existed, and I can't seem to figure it out :/ Have been living with this issue for more than a year, now it's time that it changes!

The computer is just suddenly off, and starts up again.

It's completely random, sometimes it doesn't happen for days, sometimes two or more times right after another. Sometimes right after boot, sometimes after hours, sometimes not at all. Sometimes when I am using the computer heavily, sometimes when I'm not using it at all, or only surfing, or only playing music, etc.

• It happens on both Windows 7 and Mac OS Lion, so not a OS problem. (Yes, it's a Hackintosh)
• I checked the RAM extensively, then replaced it, so not a RAM issue.
• Temperatures in the computer are all fine. No overheating.
• Used different hard drives for running the OS, so not a Hard Drive issue.
• Did an update to a different BIOS, problem persisted. So not a BIOS problem.
• Neither Mac OS's nor Windows's logs show anything. No blue screen on Win, although switched on.

My questions now:

• I tested the processor (Core2Quad) with Intel's Processor Diagnostic Tool, and it passed the test. I assume it means there can't be the processor, is that right?
• How can I check the power supply? (I don't have a spare)
• How can I detect whether it's the motherboard or not?

How can I solve this problem?

Thanks a lot!

UPDATE: It wasn't the PSU. Replaced it with a new, more powerful one and the problem persists :( Seems like my motherboard is causing this...

Answer 1

It's always the last thing you test, is where the problem is always found :-)))

Sounds like a power supply issue to me. I'd certainly swap the out for a higher wattage psu and see if the makes the system more stable. Also try adding a filtering UPS , you may be getting power spikes from the laundrette next door ;-)

Motherboard could have a dodgy capacitor or dry joint somewhere. Physically inspect the motherboard and the cap's to see if there is any bulging or leaking. In fact any damage you can see on might be relevant.

Is the motherboard properly grounded, make sure it is, also while the machine is running trying applying small amount of pressure to different area's of the motherboard (not any electrical tracks) and see if this causes a reboot. This may indicate a hairline fracture in the motherboard itself. which drags the tracks apart and cause a short/break.

don't do this if you don't know what your doing, but seeing as you built the machine yourself, i assume you know how not to electrocute yourself.

try using an external video card, as sometimes a built graphics can be cause these type's of problems.

but the first port of call would be to see how much wattage your system is running, and get a SOLID and over powered PSU for you machine, and see if clears that up.

http://www.stresslinux.org/sl/

try this and see if you can recreate the problem. Motherboards over cheaper quality can't sustain 100% cpu or bus/memory utilisation. That's why a lot of machine fall over when installing the OS because for the rest of their life they just do light tasks like word processing.

if you can get the dmesg and /var/logs before and after the crash this may show some clues...what kind of server is this?

Answer 2

Since you don't have spare parts to test this yourself, take it to a shop that does, and can swap out some of these things. I would lean toward thinking it's the PS, myself.