Mid 2011 iMac Graphics Problems with Yosemite

It's not. My problems started when using Chrome.

We're just going to have to wait for the next OS update, it looks like. 😟

It was really my Mac stable for only two days , now the problem came back again. Apple really needs to do something to fix this.

Have the exact same problem as OP. iMac 21.5 inch, Mid 2011, AMD Radeon HD 6770M 512 MB, red and green pixel boxes on the screen.

Started slowly, only happened occasionally when I was running two monitors and photoshop, along with other randoms like firefox in the background. Progressed to where I can't run a second monitor at all. Now I'm not able to do anything on the computer. It freaks out (kernel panic) within minutes of booting up. I'm not even sure I'll be able to try any of these workarounds because I don't think it will run long enough. It does this even if I don't try to run a single program. I can start it up, log in, leave it sitting, and it will freeze all by itself.

Might give Apple a call and see if I can magically find the nice person who will replace the GPU for free even though it's not covered on the warranty extension according to Apple's own website. I don't know if that's really the problem, but if it's free I'll try it before I spend a whole day wiping and reinstalling my OS.

I just install the new OS X update (10.10.2). It seems fix graphic problems with yosemite on my iMac (mi-2010) with ATI Radeon HD 5750

I turned off transparency last night and the pixel blocks vanished immediately. Then I was able to update to 10.10.2 because the computer was stable enough finally. Really hoping this is a permanent fix!

Use the update 10.10.2 since beta , and so far no correction was made ​​for my problem . Today I am working with transparency and offline using Google Chrome. Only then my machine is stable.

You should do a clean install of OS X Yosemite and then update because you're coming from the beta and that may be causing the problem.

I have had the same problem of "graphics problem" which I have reported to Apple each time it appeared.

I am now downloading the latest up date 10.10.2 which up to now has taken 90 minutes and still says 57 minutes to go! It actually went backwards at one stage from 263mb to 264mb.

I just hope this fixes the problem but I'm not holding my breath.

iMac 12,1 (21.5") AMD Radeon HD 6770M 512 MB

10.10.2 didn't solve it. I'm turning off transparency for now to see what happens. I *think* i've been having this since Yosemite, it's been getting worse. :-/

I think this just happened to me. Mid-2011 27" iMac on Yosemite 10.10.1. Had a bunch of open programs and was browsing on Safari when screen started to go in and out. When 'out' it looked like the old days of TV where you would lose a station and just get that grey snow. I quickly grabbed the iPhone and made a video. Ended up turning off the computer for 10 minutes and it seemed fine on rebooting. I have updated to 10.10.2 and turned on 'reduce transparency' in the accessibility settings. I had a Genius appt set up for today but wondering if worth doing. My 3 year Apple Care expired in July 2014...

Ignore the 'play' icon - screen shot from iPhone

If that video doesn't embed, it is here on Vimeo: https://vimeo.com/120886033

I have the same problem and I think it's related to the temperature increase.

I have found that my iMac 27" is getting much hotter after upgrading to Yosemite.

Even when putting a little extra pressure on the Mac by opening more apps and multi-tasking, the computer (and especially the screen) get extremely hot.

If I have the a/c blowing straight at the computer, the problem doesn't occur.

My biggest concern is that eventually the graphics card will overheat and blow.

Any thoughts along this line of thinking ?

RM

I'm having the same issue. Same iMac. It has graphics problems and freezes and needs to reboot almost every day. I went to genius bar last month. The apple guru reloaded the system and it seemed fine for only 3 days. After that the iMac freezes again. The issue have never been solved.

iMac 21.5-inch Mid 2011

CPU 2.7GHz Intel Core i45

RAM 16GB 1333 MHZ DDR3

Graphic AMD Radeon HD 6770M 512 MB

Same problem since update to Yosemite. UI Lags!!! Can't use a second monitor anymore. If i back to Mavericks everything works fine, smooth transitions... But with Yosemite 😢

My Mac is in the same situation. I'm using Yosemite 10.10.3 and no solution has been developed so far. I'm using my machine without the Safari and the transparency off , just so I can work .

iMac 21.5 - inch Mid 2011

CPU 2.7GHz Intel Core i45

RAM 16GB DDR3 1333 MHz

AMD Radeon HD 6770M graphic 512 MB

I have been dealing with this since my upgrade to Yosemite. I have posted to several threads and literally spent hundreds of hours trying to fix this issue. I have tried everything in this, and other threads.

None of it works.

It is clearly a driver issue. I can recreate it easily and repeatedly. I can also avoid it with certain techniques that have been touched upon here. It is NOT a hardware problem and even if it was, my Mid 2010 is out of warranty for the recall and has been since Yosemite came out after the recall expired. Apple refuses to acknowledge tens of thousands of people who have this problem.

This is why I am not buying another Apple product.

I officially give up trying to solve this problem. Good-bye apple. It was a good 4-5 year run but you became unresponsive to your customers and stopped caring about customer service. I guess it is back to DELL+Windows8.