iMac Video Card Meltdown

Hello all,

I've recently ran into a problem with my 20-inch aluminum iMac, which I've partitioned into 1/2 Mac Snow Leopard, 1/2 Windows 7 via Boot Camp. I've had it this way for over a year, and have been gaming quite heavily on the Windows side (thanks to the upgraded ATI HD-series video card I ordered when purchasing the computer), and now have it as my default startup OS.

In my first year of college, I lived in a dorm, where the computer was stationed near a window I usually kept open; it could run nearly any game beautifully, from Fallout 3 to Oblivion to Fallout 3. I often played for hours on end, and though the computer's aluminum casing would often get quite hot, it would never result in any performance issues.

However, I've now moved it into a spacious but windowless interior bedroom, though I the computer is positioned close to a door; since then, I've had the sudden black flashes on the screen during gaming and subsequent Blue Screen of Death for a few seconds, followed by a failed reboot (the computer will elicit the Mac startup chime and start some faint whirring noises, but the screen will remain black). This is only resolved when I unplug the iMac from the wall and leave it to sit for a few minutes, after which it starts up normally (albeit in the 'unexpected shutdown' screen'). This has occurred in multiple games, Left 4 Dead 2, StarCraft 2 (only in post-patch, interestingly enough), Bad Company 2 and Titan Quest among them.

After some asking around, I was told that this is most likely caused by the graphics card overheating and automatically shutting down, due to the graphical stresses of high-res gaming. Now, I'll admit that the move to a lack of air circulation in the room may have something to do with it, and that Mac may not be the ideal gaming platform, but I can't be expected to believe that my computer - once able to play Fallout 3 and Mass Effect 2 on maxed resolutions for hours on end, not a semester ago - is now incapable of running Titan Quest on lowest possible setting for even twenty minutes without melting down like this.

Hypothesizing that my fans may not be sufficiently cooling the interior, I downloaded smcFanControl for OS X and turned the minimum fan speed up to half of the available scale. This did nominally prolong my gaming time, but the computer still eventually Blue-screened and melt down as I expected.

So now, I am at a complete loss; what factors in my new environment could have caused my iMac to turn into such a wimpy grilltop? I turn to you, Mac Forums, for counsel.

Thanks for any solutions,
-Dave

For starters, it may not even be the "environment" it now resides in. You moved your iMac. (literally) It may have gotten jostled around and something on the video card (or elsewhere possibly) may have gotten lose/damaged, and now you're experiencing issues.

Having said that, maybe one of your fans isn't working? (could be just a lose plug, short, etc.)

I too, have a hard time believing that the GPU would be toast in this short of a time span. It's not impossible though....

Rizzy,

Thanks for the suggestions. My local tech office has suggested it might be a buildup of dust inside the computer, so I've scheduled to have it inspected tomorrow morning. I'll report how it goes.

-Dave

That's a possibility, but also it occurs to me that you previously taxed it to the point where it may have been getting ready to go, and the move or something related to it pushed it "over the edge."

This theory could easily be tested by just running the computer for normal non-gaming stuff and see if it behaves badly. If it does, then I'm right.

chas_m,

I'd appreciate the input, but diagnoses such as 'taxing it to the point of getting ready to go' and 'pushing it over the edge' sound a bit too shamanistic when it comes to computer diagnostics.

In any case, the computer behaves normally in all cases except when I play games, which case, OP happens.

Thanks,
-Dave

It appears that the problem was indeed dust buildup inside the computer; after lugging the heavy computer to the office, having it cleaned, and carrying it all the way back, the computer has performed close to optimum efficiency; it takes several hours of continuous gaming before it begins to get hot; of course, afterwards the screen does begin to flash black, but I'm guessing that's some permanent damage done to the video card, what with all the overheats and all.

Just curious - knowing how those are designed esthetically, how did you get that much dust in there? lol

I'd guess it was the year it spent in the enclosure on my computer desk, which had was extremely dusty and never wiped down, likely from the slit in the top back. Just curious, what is that thing for?

The slits in the back of the iMac are where the fans draw in and exhaust air for cooling.