2011 iMac 27 graphics card problem?

I have had the exact same issue for several years now (27" 2.7 GHz w/ 6770M. I took it in back for repair when it was still under extended AppleCare and they "could not reproduce the issue" after having it for a week (a huge inconvenience at the time since it was my only machine). Very frustrated, I brought it home and of course the issue returned. I have just tried to manage it the best I could for the last few years, but it has only got worse. Now that it is known issue, I am going to try again, and hopefully the fact that I brought it in under AppleCare and they didn't fix it will get them to do it for free this time. I don't have high hopes, but I'm ready to have usable computer again.

I have iMac (27-inch, Mid 2011)

and last year (early 2016) the whole screen started turning to vertical stripes. I made all the usual attempts to fix. After several days of this happening more and more frequently, I could not even turn it on more than a few minutes. I took videos and screenshots.

Took it to Genuis Bar and they informed me of known problem and said it could be replaced free if their diagnostic can show the failure. We sat there for hours and diagnostics found no problem at all. And issue was never witnessed. I showed them the video and photos all timestamped. Didn't impress them much. Left it there overnight, turned on in the back, running diagnostics repeatedly. Never showed a problem!

I was forced to take it home. An hour after using it: bang! Stripes.

How could it stay on for 24 hours at Apple Store and not last more than a few minutes at home??? Took more photos and videos.

Back to the Genuis Bar. Hours. No sign of problem. No diagnostic failures. They even said that the test was very specific for diagnosing this problem. Passed with flying colors. I complained that I'll keep making appointments every day and haul it back and forth if I have to. They said they can replace the card but I'd have to pay for it, since they can find nothing wrong. But I said this is all a known problem with this model!

Finally they caved and said they'd "take my word for it." They replaced card for free. Problem went away! .... Or did it?

Flash forward to today, maybe 15 months later. Since 6/7/17 I am having same issues again. Stripes. This time at Genius Bar they investigated kernal panic, as when screen goes stripey it reboots itself. But diagnostics found nothing wrong. Would not happen in store.

They recommended full wipe of drive and reinstall of Sierra. Must be corrupt OS they said.

Done! So happened I had a FULL Time Machine backup as of 6/6/17.

This morning, happily thinking my "corrupted OS" was fixed, I had just gotten Mail back up and it began downloading emails... Then bang!

As I write this: gray vertical stripes, this time strobing. I let it go for 20 minutes and it's not rebooting. In fact I can hear the drive working on my Mail as if nothing ever happened. Keyboard and mouse seem unresponsive.

Why does this only happen at home?? And that appears to be experience with other people also. My best guess is it's because I'm using it at home. I'm loading up RAM and CPU stress. I think card flips out after a level of resources are under pressure by some x%.

But what now?

Just completed another trip to the Genius Bar, this time to insist on fixing this problem - replace graphics card or whatever.

I said I know this is the same iMac 2011 GPU problem I had last year. So this graphics card is only 15 months old. They ran their fancy diagnostics tool and no problem. No surprise to me. I showed them a timestamped video of gray vertical lines flickering at me this morning. I said it did that for 30 minutes, and all I had done was open my Mail program. That's it. I could hear the disk still working when the screen was gray stripes and flashing.

We ran checks for a half an hour without any sign of a problem, and the Mac barely heated up.

I said "Why does my Mac get so hot at home? I've got a web browser open, email, no big deal. No streaming videos or video games or anything. It gets HOT, and then eventually the screen goes out."

They claim their diagnostics tools "applies a lot of pressure" on the graphics card, more than what my programs do, and it's not showing any failures. They ran diagnostics on the fans, no problems their either.

They asked me about it's environment at home. I said it sits on a corner desk with a hutch. Beh

It sits in a corner desk with a hutch. But behind the computer is a trapped corner area that isn't ventilated well, and they suggested that the air intake at the top is sucking in hot air blowing out the bottom and it's probably causing it to get too hot, combined with a graphics card which, while only 15 mos old, is known to fail in these Macs. It's a $550 card or somesuch.

They recommended I move the mac to a cooler area. They said it sure isn't overheating in the store.

So once again I marched out without any fixing done and came home to plug my iMac in at a temporary location where it's cool and there is plenty of ventilation.

I opened Mail and Firefox. After a half an hour it got pretty hot - though not unbearable. Screen went to gray stripes.

I DON'T UNDERSTAND. I went through this last year and this year. I hauled this thing to and from the Genius Bar maybe 8 times between both years and NOT ONCE did they ever see or detect any problem at all.

Definitely graphics card.

If you are in the UK then Apple have to replace the card under European Consumer Law. There is a 6 year cut off point so make sure you make a claim through an authorised Apple service/repair company before the six years are up (from the time of purchase or delivery).

my card failed at the end of April 2017 but because I knew nothing at the time about this and because it took several weeks to get a proper diagnoses, my iMac fell outside the 6 year cut off point by a few weeks. I made a claim but Apple rejected it, so get in quick.

A new graphics card, labour and VAT will set me back close to £600.

Apple have been incredibly unhelpful. I have been advised by them that there is no-one in their organisation who can help me. Although it seems that someone was able to reject my claim.

They did launch a return program but unless you're an Apple geek you wouldn't have known about it. They actually told me today that there hadn't been a program.

I have been an Apple user for close to 20 years and contrary to popular perception there have been a lot of ups and downs, lost work etc and poor support from Apple, but I have remained loyal.

As I will now have to replace my machine I will look at other options. There is a world outside of the Big Mac.

So it's goodbye from me.

Yep. Same issue with mine. i was told by Apple technicians that the card should last 3 years......

Having contacted Tim Cook's office I have been told that they will not pay for this replacement.

Replacing the card is prohibitive......

Following the last comment made above....

Another follow up. The artifacts and failing video card issues were manageable.... until I decided to install High Sierra. Now the artifacts are so bad that the system is nearly unusable. Hard crashes daily. Debating whether or not to bring it back for repair and pleading my case that another 6770 card shouldn't be installed, it will be my 2nd replacement.

I have a late-2011 model 6770M that has started showing these symptoms since I upgraded to High Sierra. Similar to you all, I have been unable to reliably replicate the issue. It does seem to happen more often right after the computer wakes up and usually when there read/writes to the harddrive.

I have the same exact iMac (Mid 2011, 27in, 2.7GHz Core i5, Radeon HD 6770M) with the same problem.

But it's not only this, there's some general graphics related funkyness going on.

E.g., when in Aperture, some operations (like zooming in) to the image will render the main image area of the Aperture unusable until I restart the program; images there won't refresh no matter what I do, like selecting a different image in the browser, zomming in and out, etc.

In Photoshop CS6, too, some operations will carve out a section of the image (like where a dialog box was), which will never refresh after that until I restart the program. At first I thought it was the apps not compatible with Mavericks, but now that both Photoshop and Aperture have seen updates since Manericks, and these problems persist, I'm thinking it's the OS and/or my graphics card.

There was an issue with the particular graphics card that shipped with this machine; I myself had to get it replaced several months ago. Quite annoying I must say, as Aperture and Photoshop are pretty much all that I intensively use this machine for.

Yes close ALL APPLICATIONS before trying to Install Mavericks. You can't have applications open while trying to do system UPGRADES or UPDATES. Restart your computer and start from scratch.

This is such a relief for me to see this posted, as I am having the same problems. I've been dealing with the multi-colored squares and flashing blocks for a few months now, but they've been increasing in severity. I run Windows through Bootcamp and it is also 10x worse when I'm running Windows, to the point where I can't even use it sometimes. I can't deal with it anymore when it's interferring with getting work done. I've been considering wiping the system and reinstalling everything, but I have a feeling that won't fix the problem.

My Mac is also from 2011, 27in with 2.7 GHz Core i5 and the Radeon HD 6770M. The issue happens on both the Mac OS and Windows.

Oddly enough it was a replacement for my 2009 Mac that died; the Apple techs couldn't figure out what was wrong with my old one, even after replacing a few parts, and gave me this one as a replacement. :\ I really didn't want to go through this again only 2 years later.

Message was edited by: MerMc I should add that I'm running Mac OS X 10.6, not Mavericks, which is the new OS? I didn't even know they had announced another.

I also have the same problem under Mavericks with the same iMac and Gfx card. I've even had the computer crash hard 3 or 4 times with a GPU hang and other gfx card related crashes. This continues under 10.9.1, but the drivers haven't appeared to have been updated.

The quick way to clear the artifacts when they occur is to trigger Exposé for showing all windows for an app. The crashes seem to come after a few days of not rebooting so rebooting often may be advisable.

I've reset the PMU and NVRAM which may provide some temporary relief, but it doesn't last.

Everything was fine before Mavericks, so it seems likely that it's sofware related unless there's a widespread problem with this card that just now coincidentally coming out.

Reading other threads it seems that similar gfx cards from the same time period are having issues on Macbook Pros which they've dealt with by switching off the discrete gfx option, which we can't because it's our only gfx option.

I often work with 2 Safari windows open covering my screen and I find that the gfx glitched happen less often in that configuration.

It's all just stressful and annoying and I hope they come up with a solution soon.

I don't think there is going to be a software-based solution to this. I'm going to be out of the country for 3 weeks starting 12/30. I'm gonna take this iMac to the Apple Store and tell them to give me a complete fix by the time I get back.

I have the same since the 10.9.1 Mavericks update.

First some very heavy funky colored flickering. Then suddenly a light gray screen, and my Mac hung.

The logs says
GPU hang: kernel[0]: Trying restart GPU

it was so bad I had to do a hard reboot.

Then I heard the startup sound a couple of times, repeatedly.

After a few hard shutdowns (keeping the power button pressed) it rebooted again.

Gave me an awkward feeling for 5 minutes... This never happened before.

My Mac:

MacBook Pro Late 2011

OS X 10.9.1

Processor 2.2 Ghz Intel Core i7

Memory 16 GB 1333 MHz DDR 3

Graphics AMD Radeon HD 6750M 512 MB

Serial nr C02GQ17DDV7N

I'm seeing similar issues, random color blocks dotted on portions of my screen, general black flickering along lines of windows. It started when I went to 10.9, has actually increased with 10.9.1.

I'm going to try an NVRAM reset & possibly even SMC reset. I know in past sometimes clearing those 2 fixes it when specific to issues following an upgrade. Overall I am loving the performance of Mavericks, hopefully Apple can find the root of this issue soon. Wondering if it could even be a firmware update that is needed & not the OS.