Specs as follows:
Gigabyte GA-EX58A-Extreme motherboard
Intel i7 950
18gb DDR3, 3x2gb + 3x4gb
AMD Radeon R9 290 in when failed. Tested Radeon 5870 to see if graphics card was to blame.
Many hard drives.
850w power supply.
Behaviour when failing: In Windows 7, 64, light duties ... programs begin not responding, mouse still moves, task manager won't appear on ctrl+shift+esc ... so I hard reboot.
On reboot, beeps, goes to BIOS splash, does nothing, unresponsive to del, tab, F12 etc.
On hard shutdown, same.
On successive hard resets with R9 290 installed, inconsistent long tone sounds before going to BIOS splash.
After replacing with 5870, no long tone.
Then in the morning I got the following behaviour:
BIOS Splash hang
Pre-BIOS hang
Got to WinLogon - USB KB and mouse input failed
And then I finally checked liked on another pre-bios hang and after some confusion with orientation and my cell phone camera, I got this partial read out:
88,C1,bf,b5,C1,88,b5,b8,b9,bf,c3,08,18,25,00,26,2b,28,33,49,48,50,58,52,75,8b,88
I also noted 4 of 6 LEDs next to the 6 occupied RAM slots and full LEDs up top ... presumably for the CPU.
This is an old system, that hasn't been overclocked, but has been worked hard. After a recent move, sound stopped working inexplicably. I fear the issue is board related. I have a RAID 0 in there. Recovery of the data on that will be the top priority. I have a backup PC to work off.