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iMac (27" mid-2011, i7, Radeon 6970M) freezes up starting games

When I try to start up a graphics-intensive game (e.g. Deus Ex: HR, Assassin's Creed), the graphics completly freeze up, and the computer requres a hard reboot.

I have Windows installed on another partition on the disk, and the same issue occurs there, at least with games (the only thing I run on that side). The screen goes "blank" (actually, grey with lines running up and down), and requires a hard reboot.

What's odd is that this really points to some sort of problem with the graphics card, but Apple Hardware Test reports no issues with the hardware. I've zapped the PRAM several times to no avail (reading somewhere that that would help), but it hasn't

Any ideas? Anything else that I can try to narrow down the problem before I bring the computer to the Apple Store for repair?

iMac, OS X Mountain Lion (10.8.1), 27", Core i7, Radeon 6970M

Posted on Aug 26, 2012 8:56 AM

33 replies

Oct 20, 2012 11:23 AM in response to gdecesare

Hi guys.

Hope your system is ok now. Just passed by to give a update on my situation, as a matter of information.

My mac doesn't even start anymore. So, it doesn´t seem to be heat related (I still accept the possibility that it was heat related, and it degraded into somethig else).

And the applecare center are kinda hard on my country, there are no apple stores, only third party companies that are signed by apple.

Also, there was a problem with a few hard disks on some macs, and I got an e-mail saying that I should change mine (for free, it´s a recall), I hope that solves the issue. Gonna drop the computer at that store this week.

I intend to try to boot from the install system before that, if it is a disk problem, that system should boot from another disk, I believe.

Even so, I had another imac in the past that lost performance in games after a while, so I bought a PC for that now (that´s where I´m typing).

I intend to repair my mac anyway, or buy a new one in a few months (worst case scenario). The PC should be for games only, I don´t intend to work on a windows based machine anymore, MacOS is the best thing about apple, imo.

I´ll let u guys know of any news. Hope my info helps anyone with a similar problem.

Sorry for any English mistake, it´s not my natural language.

Denus01

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Oct 20, 2012 12:16 PM in response to Yorick_ibazar

Hi,

Yes, it's working so far 🙂

Well, my system was like yours, first it had some lockups (heat related or not, I don't know) and after a while, the system wouldn't boot up at all.

At the first repair, the mainboard and videocard were replaced, but a week after the repair, I had similar video issues and the videocard had to be replaced again.

If you got no power from the usb ports, then you can almost be sure the mainboard is dead (too).

Btw: English is not my language either, but I'm certain we are doing better than some native English posters 🙂

Denus01

Level 1

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Oct 22, 2012 6:09 AM in response to Denus01

Bad news: the issue is back!

And the system must be repaired one other time before a replacement can be done by Apple.

3 repairs in one month: that's epic!

iMac (27" mid-2011, i7, Radeon 6970M) freezes up starting games