Summary -- games continue to run on automatic loops for some graphics and animations while the sound and any new instructions into the game environment stop. Graphics display no signs of corruption.
Detailed description --
Playing a game, usually one with a reasonable amount of sophistication (and demand on hardware), the sound will often stop.
What's really strange is what else happens when the sound stops. Any new instructions for the game fail to load. However, the graphics and whatever routines are running at the time of the freeze will continue to run.
For example, a turret firing from a bunker in a WW2 shooter continues to spray out bullets in a set pattern. But the sound stops, and all new movement inputs (both for the player and the AI) cease.
Sometimes during cutscenes, the whole thing will freeze except the animations (like water flowing) and, without sound, the subtitles will continue to stream.
A specific example of this is at the opening scene of Battlefield Bad Company. Your small team is on a boat heading into a Japanese POW camp and a mate is speaking with you.
The game will freeze the sounds and the boat will stop moving. But the smoke from my mates cigarette will billow onward, the water will bob the boat up and down, and the subtitles for the opening scene will continue to flow as if nothing has gone wrong.
There are no screen graphic corruptions.
This is not a game-specific event, but I've reproduced it in many games, even titles as benign as The Sims 3.
Often the freeze will recover after 30-60 seconds, and then re-freeze, until a total system crash occurs.
Well I just got a big clue running these tests. Firstly, for both CPU and GPU stress tests yielded very reasonable temperatures. The CPU hovered around 55.C at it's height while the GPU didn't break 73.C
What was most remarkable was that only the Directx9 tests in OCCT would work. Initiating a DirectX10 test immediately crashed the whole system every time.
Then when the system tried to restart, it hung on the BIOS.
After reset, the BIOS warned me that motherboard surge protection measures had been initialized after power surges were detected on the last boot.
Rebooting again got rid of the power surge warnings and the system booted normally, but only 3 cores out of 4 on the CPU were enabled. I had to manually reset that in the BIOS to get 4 cores back online.
All attempts to retry the DirectX10 test in OCCT yielded an identical sequence of events.
The card is a Radeon 5700. Drivers and DirectX are up to date as of July 2012, but I have been without internet access on that computer since that time. CPU is Phenom II 4core.
Memtest86 failed to load on a USB boot stick. The MOBO booted from the stick but I got a Linux command prompt and nothing happened from there. I'm probably doing something wrong on that, but I have no idea what.
Nevertheless given the catastrophic results of the DirectX10 tests and the notices about power surges I think we probably can guess this is going to be a hardware issue, relating to either the graphics card or the power supply.
No other problems come up, and again, the temperatures are all very reasonable.
I've had problems with it crashing during games and then failing to reboot since I got it over a year ago, but nothing this severe. Since the past two months things have gotten worse (as described above). Technical support from the company that sold me the computer is incompetent. First they had me replace the hard drive, and then most recently the motherboard. Since the problems persist I have figured out that obviously I'm on my own in resolving this.
I'll get the PSU info for you and post it asap. I don't have it handy right now.
I can't find any professional reviews of that power supply but it does look like a bad one, I suspect it is the most likely cause of the problem but it could still be a bad graphics card or RAM. Do you have any way to swap any parts?
I haven't got a chance to swap the power supply unit. However I did try lowering the clock speeds on the 5700 from their factory defaults to the lowest settings available in the ATI catalyst control panel to 500Mhz and 1200Mhz (1200 was already set as the memory low.)
Then I ran the OCCT DirectX10 test and had no issues at least for the first 10 minutes.