Mid 2011 iMac 27 Massive Crashing

[Beerco]

Hi all,

Getting sort of desperate here. I've got an mid 2011 iMac 27 (12,2) that's suffering from massive crashing. I run time machine so I'm not too concerned about data. Running Mavericks right now for an OS

What's happening is that from time to time (occurring more frequently now) the screen will freak out and go to any number of different states - either pink with lines, white with lines, flashing like a strobe etc. Usually, the machine will not re-boot with a normal start after such an event. Here's what I've done so far:

Safe boot - works maybe 50% of the time. Running a verify disk tells me that the disk is fine. I repair it anyway. There's usually some permission errors. Re-boot usually works.

I have 16G of memory so I've been swapping it out to see if that's the problem. 8G was from Apple and 8 from somewhere else. Samsung is one of the brands and I forget the other. Seems to crash irrespective of which ram is in there.

I ran the Apple Hardware Test and it freezes at about 75% in of the probing hardware. When it locks up the space behind the mouse pointer turns red.

The only things I haven't done so far is to wipe the disk and re-install OS X. It looks like because of the age of my machine, I'll have to go Lion and then upgrade to Yosemite - is that correct?

I'm going to hold off a little bit on that to make sure I can do everything right.

Any other advice? Due to the problem with the hardware test, I'm worried that something is screwed up with my Logic board or perhaps the GPU. When the screen crashes, I can still hear the hard disk crunching away in the background but it never recovers. Sometimes the machine will re-start on it's own if I leave it alone long enough after such an event.

Please help!!

Thanks!

 

[Brian Y]

That's the GPU.

Do you have the high-end one by any chance? The 6970M is known to fail, and is covered for 4 years from the date of purchase (so they should all still *just* be covered). https://support.apple.com/en-us/HT203787

 

[Beerco]

Thanks so much, it is indeed the high end one. I'll contact Apple right away!

Again, can't thank you enough!

 

[Beerco]

Follow up (about a year later) - it was indeed the 6970 that was failing. I had to show proof that it was failing to get them to replace it but it finally did fail in the store and they replaced the GPU for me.

Thanks!

 

[Firebrand]

Hopefully better (more reliable) gpu’s on the horizon

 

[Razzerman]

Wow...that's interesting. Can I ask where in the world you are Beerco, as we've have four similar machines conk out at work?

 

[Beerco]

I'm in the U.S., Metro Detroit area in Michigan to be exact.

Strangely, in the last couple weeks I've had some glitchy behavior from the video card again....hopefully it will be ok. Computer isn't crashing but I'm getting small versions of whatever is open in my browser in the upper left corner of the screen....it flickers in and out and then goes away.