Hi. My main computer consists of:
Mainboard Gigabyte GA-B75M-D3H
CPU i7-2600 (Sandy Bridge)
RAM 8GB (2x4GB) RipJaws FD-10666CL9D-8GBRL
PSU Seasonic X-560 80 PLUS GOLD
2TB Hard Drive and DVD Optical Drive.
Using i7 integrated graphics.
A few times, the computer has crashed with the following symptom: the screen suddenly is filled with random, various coloured short lines and dots changing at a very rapid pace, and the machine is completely locked up--it must be reset (reset button) or powered off.
Sometimes I have the computer playing music, but most times not. Previously when the crash occurred, if there was music playing, then in addition to the screen going wild, the sound also went wild and became just a bunch of very loud rapidly changing static--kind of an aural version of what was happening on the screen, as though the CPU had run amok.
When this has happened previously, doing a reset, or a power off and then on, has restored normal operation. The machine runs cool (CPU 28-31 at idle, a few degrees above ambient, and never really reaches full load), and the case is clean.
But yesterday when this occurred, I pressed the reset button, and the screen went black (as it normally does at the beginning of a restart), but it did not restart; the monitor remained in sleep mode (black screen, power button blinking), and after about ten seconds, the computer powered off, and then five seconds later powered on, and again after ten seconds powered off and five seconds later powered on, and this continued until I held the power button for five seconds to shut it off and make it stay off. It was as though it was trying to reboot (case fans spin, CPU fan spins, hard drive and optical drive seek) without success (there was never any signal to the monitor).
I replaced the power supply with a 610W PC Power & Cooling unit, since I had it available, but received exactly the same symptoms. So that rules out the power supply, and I doubt the hard drive or optical drive could cause such symptoms.
That leaves the mainboard, the CPU, and the RAM. I just last week ran MemTest86+ for move than 5.5 hours, completing more than five complete passes, without a single error.
So, I need some input. What should I try next? I don't have either a spare CPU or a spare mainboard, so replacing either of those would mean buying a new one (expensive!), and also don't have another system to test the CPU in.