Q: 2011 iMac 27 graphics card problem?

same iMac (27-inch, Mid 2011) same issue.  AMD Radeon HD 6770M 512 MB video card is the problem according to the Apple store.  Past warranty however they did offer a $150 fix- replacing the original Video card with the same thing.  I figured I might upgrade the card to 1 GIG.  Any advice brethren?

Same problem cropped up here.  iMac 27", Mid 2011 with AMD Radeon HD 6770M 512 MB.

GPU hangs and can't restart... causes a cascade GPU failure and blank screen for me.  It is NOT a temperature related problem.  And other process can still be running, including sound and voice chat... you just can't see it!   Occasionally will cause complete system crash.   Very disappointing.

From system Log:

5/12/15 6:38:55.000 PM kernel[0]: Trying restart GPU ...

5/12/15 6:38:55.000 PM kernel[0]: [1:0:0] Failed to reset hung GPU! result=151 ulResetBlockBitmap=0x00000100 ulResetResultBitmap=0x00000100

5/12/15 6:38:59.000 PM kernel[0]: [1:0:0] GPU HangState 0x00000000, HangFlags 0x00000006: IndividualEngineHang 0, NonEngineBlockHang 1, FenceNotRetired 1, PerEngineReset 0, FullAsicReset 1

I am also having the same problem with the same machine Mac Intel 2011 mid, same video card why hasn't Apple realize this is a recall problem if all the same year same video card having the same issues.  Class action law suit might help them fix this problem or the whole world could know how crappy they are building there product in order to get them out quicker to compete with PC that are working and cheaper to fix when they do have problems.  Why pay triple for apple for less of a product.

Hi all,

I'm suffering exactly the same issues, running a 21.5-inch, medio 2011 iMAC, with... a AMD Radeon HD 6770M 512 MB ! The problem started about 1 year ago (August 2014), I believe after an update to OS X 10.9.4.

The scenario is alike as described in this post (and in similar post: Red and green square dots?):

- colored squares appear on the screen,

- with some bad luck it's like ' a waterfall', and the screen is full of them,

- if you're lucky: they disappear

- there is a much higher probability that they appear in iPhoto (which I use very frequently...)

- in 70 % of the cases, the system crashes completely: hanging ...

- no entry in logs is made

--> frustration guaranteed !!!

I brought my iMAC to an Apple repair-centre here in Belgium; they tested the machine for 1 week and could not find anything :-( also extensive HW-test didn't show anything.

Any help is welcomed...

Peter

I am also having the same problem with the same machine Mac Intel 2011 mid, same video card why hasn't Apple realize this is a recall problem if all the same year same video card having the same issues.  Class action law suit might help them fix this problem or the whole world could know how crappy they are building there product in order to get them out quicker to compete with PC that are working and cheaper to fix when they do have problems.  Why pay triple for apple for less of a

Maybe I have found a really simple solution to this problem: I have been experiencing the same problems for almost 6 months - since upgrading to Yosemite. The only thing that has helped (for a short while) has been, just as some other people have pointed out, to re-boot.
But about an hour ago I checked the settings (and since I see these in Swedish, I am guessing the English words): Apple symbol-> About this computer - Monitor (or Screen) -> Color.

Once there I changed the profile from "iMac" to "iMac calibrated" and the problem with the flashing squares went away instantly. The screen has been clean since one hour. The longest time in six months!
Will post again if the problem returns. Hopefully it will not.

I have gotten my problem with the screen fixed, I took it into the Apple store and they were able to tell me what the problem was. All it was that when I first upgraded to Yosemite it did not load correctly, so they uninstalled Yosemite back to Maverick then upgraded again to Yosemite it's been more than 2 months without any problem.  Make sure you are using Time machine and back up all your files before doing this process, remember that any software problems, you can get fixed at the Apple store for free as long as it's thier product. Good luck God bless...

I wanted to follow up to this as I just picked up my 2011 iMac from the Apple Store. I finally had enough of the artifact issues I have been having off and on for a couple years now. There is clearly a problem with 6770m hardware but unfortunately, I couldn't get them to cover the repair since the official recall was for the 69XX models. The good news is that although I had to pay to fix it, they replaced the faulty hardware for $150 including labor! It was ready in 2 days and the process couldn't have been easier. The Genius diagnosed a bad video card within minutes and I was pleasantly surprised at the repair price ($112 for a new 6770 board.)

I tried hard to convince myself it was a software issue but sorry to say folks, these are balky models we have. Get it fixed for good and save yourself the stress! For the record, the "reduce transparency" setting allowed me to put things off as long as I did- that was the single most effective tweak that reduced the artifact problem.

For what it's worth, I have a Mid 2011 iMac with 6770M GPU, 3 1/2 years old.  The GPU failed first with distorted blocks, and quickly deteriorated to vertical green bars at startup, to the point that the OS wouldn't boot.

I took it to my local authorized dealer and after diagnosing the issue and contacting Apple they said it was covered under the replacement program, even though it's a 6770M, and the GPU was replaced for free.

So it seems at least some 6770M GPUs are covered under the 6790M replacement program.  It's worth it to take it in and let them diagnose the problem.

Since buying iMac 27" in jan 2011 I have had the same problems with random coloured pixels, flickering, lines etc

Anyone have a fix?

The fix for me was getting the graphics card replaced.

Thanks

This iMac has also been really slow since I purchased it, so could be related to the graphics card problem

How did you get the card replaced?

Assuming you bought it new in or around 2011 and it's been slow since the beginning, you may just need more RAM depending on the base amount of RAM at the time (2 or 4 GB probably). Also, make sure using the Activity Monitor app that you don't have a process constantly using CPU or Drive Activity. A bad background app could slow everything down. Other possibilities is too full of a hard drive. Things are smoother if you still have at least a couple hundred GB free, Worst case would be a failing hard drive which would entail making sure you have a backup and replace the drive.

For repairs you could take it in to an Apple store or a local certified Mac repair place that you trust and/or has good reviews which could be cheaper.

I started getting this issue earlier this year. iMac (27-inch, Mid 2011) 2.7ghz i5, AMD Radeon HD 6770M 512 MB, Mac os X 10.11.3. The screen artifacts seem to happen more often when the system is cold or if the screen is asleep for a long time. I took the system apart and re-applied thermal pads/grease to the GPU but it didn't help. Oddly enough, booting the Mac into save mode then rebooting seems to postpone the affects. Ran ASD/AHT, no problems found.

So I took in my 27" iMac i5 3.1 (mid 2011) with a similar issue, although it never really does the same thing twice.  One time it looks like scrambled pay channels, one time it has screen tearing, this time its flashes to white, then back to the screen which is also torn.

I explain the issue over the phone, and the two apple reps I speak to are awesome.  They say "just bring it in" and "they can replace the graphics card" under the "quality program" (I guess they don't want to use the word recall anywhere?).  So I bring it in to the genius bar, they run a software test...it passes.  The guy there was super nice, so he offers to "stress test" it by opening up like 9 Marvel movies at once.  It cooks for 10 minutes then the screen gets pixelated, and torn.  He reboots launches the software test again...and it passes. 

He told me that there is something definitely wrong with the graphics card, but it isn't the particular issue under the "quality program"...seriously?  This card fails in "different" ways its that bad?

The kicker is when they told me I could "recycle" the iMac to PowerOn, and put that money towards a new one.  I then told them that THIS iMac is a "refurb" from poweron and its a day old...

He then looks up the history somehow and says, yup, it looks like the previous owner had it in for the same reason last month.  Why would they let a known faulty computer be sold off as refurbished?  This is so shady its not even funny.  This video card can't cost more than $50 to make, from a computer that originally cost $2,000...this doesn't exactly motivate me to buy a new one.

I still have my fingers crossed because they were nice enough to keep it for a few days as an "extended check in" to see if they could get it to fail the software test. (I'm hoping its not just sitting in the back unplugged, but whatever).  At least PowerOn is being cool and offering a full refund, even though what I really want is a working computer.

Here is a video of my video card that "Passed" the software test...

https://www.youtube.com/watch?v=iF7bcZ2gKSI