2011 iMac 27 graphics card problem?

I have seen the same issues with a 2010 mid year iMac now and there is a pretty long thread now of troubleshooting. However as far as I can tell so far there is not a concrete solution to fixing the issue. Maybe some of the troubleshooting, comments etc will be helpful?

My display looks somewhat similar to the original post but is highly variable. Interestingly I do see a similar pattern of the square clusters. If looking from the top of the screen downward the clusters show up in somewhat organized rows. I also see that on mine and they are spaced out in a simliar manner. The quantity of flashing squares per cluster seems to vary quite a bit. I have no idea of the paragraph adds any useful information, just something I have noticed.

Here is the link to the 2010 multi-colored flashing blocks issue:

https://discussions.apple.com/thread/3867557

My iMac Stats:

27-inch, iMac Mid 2010

Memory 8GB 1333 MHZ DDR3

Graphics ATI Radeon HD 5750 1024 MB

OS X 10.9.1 (13B42)

Processor 2.93 GHz Intel Core i7

I had the colored blocks problem sometime soon after upgrading to Mavericks. I was convinced it was a GPU malfunction. I took my iMac GPU out to inspect it before I contacted Apple Support (dumb move FYI). Apple Support suggested I reset the SMC and PRAM. But by this point I already had my iMac completely dissembled. The original thermal paste job on the GPU to Heat Sink contacts looked terrible. I'm not sure if it was refurbished or if Apple did it. I cleaned and replaced the thermal paste carefully on my GPU and reinstalled it. I reset the PRAM and SMC on restarting. The blocks appeared for the first few seconds of boot but haven't returned yet. A few days of normal use have passed and still no blocks. Not sure if it was PRAM, SMC, or the Thermal Paste Job. Finger crossed I think it is fixed. A new GPU runs around $500, probably more.

My iMac Stats

27-inch iMac Mid 2010

2.93 GHz Intel Core i7

16 GB 1333 MHz DDR3

ATI Radeon HD 5750 1024 MB

OS X 10.9.1

I have just seen this for the first time on my 27" iMac. I don't use it very often since I'm on my MBP most of the time but this is a new phenomenon and I've had Mavericks installed since it came out. Has anyone seen any progress on this on another thread maybe?

Model Name: iMac

Model Identifier: iMac12,2

Processor Name: Intel Core i5

Processor Speed: 2.7 GHz

Chipset Model: AMD Radeon HD 6770M 512MB

Yup, after going back and forth, Apple Store finally replaced my logic board and the Radeon graphics card (though it's the same 6770M), and then and only then did the blocks go away. You need to be persistent; the issue apprently doesn't show up in any of their diagnostic tests, so take a video of what's happening, and convince the Genius that it's definitely a logic board / GPU issue.

I ended up getting the graphics card replaced at the end of December and it's been fine ever since.

Same problem here, mid 2011 27", Radeon 6770, Mavericks, etc.

The problem may be getting worse slowly and mainly appears on medium gray regions windows which have been static for a while, and is particulary strong on the external Dell monitor - typically toward the right sides of the screens. If you move the window, it stops for a while. Checked internal temps, screen saver mode, nearby cellular signal & RF sources (iPad, iPhone), second monitor connected or not.

The pattern of blinking seems to repeat: a period flickering followed by shorter period of very fast flickering, which reminds me of the sound of an audio noise problem I had when a cell phone was near my Mac. So far, the noise problem does not appear when the iPhone (T-Mobile) and iPad (Verizon) are off. The problem appears if I turn on the iPhone, however it does not go away when I turn off the phone, unless I also move or update the afflicted window (iPhoto's gray background is a good example). Only one day of experimentation with this, so it is probably premature to conclude that RF interference is a factor.

This has been going on long enough that I can't associate it with any system changes, however I've had the phone and pod for a while and I don't think it appeared when they did. If it is indeed RF related, then that leaves three possibilites: (1) I changed something, such as an OS level, and didn't associate the problem with it, (2) the RF interference is increasing or, (3) the iMac is becoming increasingly sensitive to the RF interference.

Anybody able to validate this? I'd hate to crack open my iMac and put in a new GPU only to find it wasn't the root cause!

Spoke too soon. No cell phone RF overnight but the flickering pixels are back in force.

So no I was wrong. I ended up replacing the GPU before this was fixed. Super weird that the repaste job temporarily fixed the problem. Replacing the GPU yourself is pretty easy BTW. New GPU ran me $539 shipped on eBay. Ouch!

Satoru,

Was it covered under a warranty or recall? If you had to pay for it, what was the cost?

Ok so I have been having this issue for maybe a month plus now. It didnt start that bad, just randomly then it would go away. Lately it has been so bad that I thought it was the thinderbolt display that is also attached that was causing it. I removed display same issues but again worse. I called Apple and we attempted to do a screen shot of the issue, and every time I tried this it went away. I noticed it then only started when I launched a new tab in safari (I will not allow firefox onto any of my machines anymore). We did a hard drive check and noticed that there was a corrupt setup, 34 registering out of 35. It did a repair and so far no issues with heavy internet usage. I suggest trying the screen shot to figure out if its hardware of software.

A replacement GPU solved this problem on my Mac. I was able to capture QuickTime movies of the pixel flicker, but it required a lot of waiting since any screen refresh or new window activity would stop the flicker for a while. Basic diags at the shop showed no problems. The repair was done by Apple under extended Apple Care warranty.

BTW, I was very happy with this support program. The quality of help was up to the tasks at hand. I'll buy it for my next Mac, which may not be any time soon now that mine is back from the brink.

I have a mid-2011 27" iMac i5 with the Radeon HD 6770M. I suffered from blocky artifacts for the last year-plus. I had them under 10.8 and now under 10.9. The solution to this problem in my case I haven't seen mentioned in these threads- I replaced the RAM. At some point a couple years back, I took RAM from an older 2009 or 2010 iMac and upgraded my 2011 machine. It was 4x2GB modules- Samsung M471B5673FH0-CH9. With those gone and double the memory, the problem disappeared and everything has been fine for over a week. I had the issue constantly to that point. For those that have tried everything, try swapping out your memory and make sure they are to the 2011 spec. The old sticks were 10600MHz DDR3 and the new ones are 1333MHz.

It's a graphic card issue. The mid 2011 27" iMacs, 2,1, had a recall that was good up to 3 years from the purchase.

iMac (27-inch): AMD Radeon 6970M Video Card Replacement Program

Although the 3 year limitation has long passed I'd contact Apple and see what can be done. I just got under the 3 year limit with my iMac.

This is true for 6970M cards, but I have the Radeon HD 6770M which had problems so far solved by new RAM.

We wanna a recall!!!

Some time ago, they call recall for the i7 models from 2011, mine is a i5 from mid 2011.

After 3 years of normal use, My machine start to get worst every day. But isn't only the squares pipocating on screen, it lock and freezes, and the only way to use again, is with physical restart.

I call for phone support on Brasil, and the operator checked my serial and told me that mine isn't on recall.

Sad, because this is a malfunction, and need to be replaced.

Apple before Steve jobs, was more serious then now.

I wanna my money back. Or a new machine without bug.

3 years is a young machine. In the past, mac works for life. I see a lot of power pc still on function.

This is not a user caused problem. A lot of people complain about the same defect.

This is not a cheap machine!

We need to be heard! Where is that Apple from Steve?

Where is my recall, APPLE????

Shame on you!