Imac display issues following Yosemite upgrade

If your iMac is in the range of serial numbers Apple has determined is eligible for a free repair, they will replace your video card for free. If it isn't, they will replace it and charge you.

The Genius Bar at the Apple Store ran a couple diagnostics that the machine passed. They said the replacement program is dependent on the computer failing the tests.

The did keep it and will run a video stress test to see if the artifacts return, if they do then they will replace the video card under the program.

If they can't reproduce the problem, take a screenshot of the artifacts when they show up again. Then take the iMac back to the Apple Store and show them the screenshots.

Rich, just curious have you tried checking on "Reduce Transparency" in Sys Prefs -> Accessibility? I can create the display issue just by unchecking that, and they go away when I check it back on.

Yes, I did turn off Transparency but just a little while before I brought it to the Apple Store. They have it now for a few days...

iMac 27" mid-2010 with ATI Radeon HD 5750 1024MB graphics card.

Thought I'd chime in here.

I'm having the exact same problems as everyone else here with the flashing square storms. It didn't start until I upgraded to Yosemite, it was fine before.

And, interestingly enough, the machine is dual boot with Windows 7 and I've *NEVER* had graphic problems in Windows 7.

It's definitely a Yosemite problem. Don't think I'll have any luck taking it in to the Genius Bar since it's so old so I'm looking and probably downgrading (fresh install) back to Mavericks unless Apple is willing to step up and actually support it's customers.

Well...

Just got back from the Apple Store with my iMac. They ran a graphics stress tester for 3 days straight and no occurrence of the issue came up. I had left the computer with them leaving Reduce Transparency checked then after a day and a half I remote accessed and un-clicked it.

I watched the stress test for a bit (woke up at 0200 and couldn't sleep...) and with all the colors and motion I am sure the video card was being worked hard.

Interestingly, they also ran a hardware test that showed my hard drive was ready to fail. Looks like that SSD replacement that I read about on 9to5mac is in my future. I could have the AppleStore replace the hard drive for $200 or get a 1TB SSD and do it myself for $400.

that worked for me - thank you!

I took my macbook pro into the genius bar last week. They ran the tests and it was all OK - they said. I had a screen shot of the problem, so they took the machine and wiped it, loaded maverick, and nothing has gone wrong since then. not going on to yosemite until they fix the issue.

Here's my final word on this problem.

I just had my iMac repaired. I took it to an authorized service center. It cost me over $500 to repair, including a $100 rush fee because they were backlogged by about four days. I did this because I can't drag a heavy 27" iMac through a mall parking lot and through a mall.

Some people here were arguing with me when I maintained this is a hardware problem. I didn't want to get into an argument because there isn't any point, but the tech who repaired my iMac said it's the video card. He replaced the video card. My iMac works fine now.

The people who said it's Yosemite are wrong. Yosemite places a greater load on the video card, which is why the problem showed up in Yosemite. Apple knows it's the video card, which is why they have replaced the card for free on some models. If it was Yosemite, the artifacts would never have started showing up on my machine in Mavericks (it got worse in Yosemite).

Apple should have replaced my iMac's video card for free, but I had the wrong serial number. My Mac is fixed. I'm moving on.

No one is going to fix the issue until you get the video card replaced.

That may have been true for you, but it may not be true for everyone. I respectfully disagreed with your assessment because you hadn't provided any evidence (just because a similar series of hardware had issues doesn't prove anything). At the same time, I also believe it's entirely possible your scenario may be different, because computers are complicated. Please consider that possibility.

Coincidentally, tonight, I decided to get off my butt, put my money where my mouth is and Bootcamp Windows 8.1 Pro with my MSDN access on the troubled iMac. It's running just fine. On the exact same machine. I have the FurMark gpu stress test running in the background. There's no way Yosemite is putting a greater load on the video card than that is. But just to be sure, I plan to leave it on overnight.

Meanwhile, the glitching under OSX is still rampant. It can be the typical square glitches to a total failure to paint any apps properly (the dock sometimes turns into a giant unpainted rectangle for example).

Anyway, for anyone else that's interested, I'll update if Windows survives the night. If it doesn't, then I'll really believe it's hardware. If it does, I may or may not revert to Mavericks to really test the software hypothesis, but it's going to look pretty bad at that point.

Regardless, I'm planning to take it in to an Apple Store on Monday. I'm not sure how they'll reconcile the fact that Windows is running just fine on the same machine (unless proven otherwise between now and then), but I plan to boot into both OSes right before their eyes. Though I suspect they'll just shrug their shoulders and push for a hardware replacement anyway.

Here's my latest update: I left the fur gpu stress test on, and windows 8.1 never crashed for the 3 days it was on. The glitches never manifested itself during active use, either.

However! If I let Windows go to sleep, and then woke it up, there would be the same graphical glitches. Although they would promptly disappear and never reappear, and the system would never crash, I think we can all agree that points more definitely towards the hardware. I'm not sure why a stress test can't seem to bring it out, but a wake from sleep can, but that's something only an apple engineer could answer (i.e. we'll never know).

I'm bringing it in to the store tonight.

I have a mid 2010 i7 with 16 GB RAM, using ATI Radeon HD 5750 1024 MB graphics card, Solid State Drive and 2TB int hard drive that came with the iMac.

I was the happiest of users when using 10.68 OS but due to encryption requirements (Gov't) and my dislike for all OS after 10.6, I upgraded to 10.10. Computer operations went from lightening fast to just acceptable and the graphics issue with pixelation that would change with every attempt I made to close windows was strikingly bizarre and forced me to hard reboot. I noticed also that my Activity Monitor memory which as always with at least 6 GB of free RAM went to 1-2 GB of RAM with far heavier use by apps that never were problematic with 10.6, e.g. Sophos, CrashPlan.

I called AppleCare and spoke to senior tech who advised me that my graphics card was being stressed with too little free Memory. I uninstalled Sophos and also uninstalled CrashPlan. I did not have heavy pixillation but instead noted only green pixels at the top of my primary iMac and secondary LG monitors. My Mac Users group advised me to go to Safari and shut off extensions and also to go to Accessibility and change to reduce transparency. I will say that so far, no pixellation and my computer is operating better. After uninstall of the two apps cited above my free Memory is more in the order of 4-6GB.

I think Yosemite is a terrible OS. I am of the belief that the last solid OS was 10.6. I had to pay for major app upgrades e.g. Acrobat Pro Professional and lost huge amounts of time with these pseudo-improvements. Evolution should not mean Devolution (sic Devilution).

Right now my monitor is behaving itself and the computer operation is better. As a medical professional who uses his computer extensively for caring for cancer patients this "inconvenience" has resulted in approximately 100 hours of wasted time + a huge emotional drain. Steve Jobs, I miss you.

Yes, I, too, have been reading responses on this forum with lots of people blaming Yosemite. Of course, since this is the "display issues following Yosemite upgrade" forum thread.

However, I've been having these problems for a year with my 24", Early 2009 iMac, and Mountain Lion. It crashes several times a day, to the point it is unusable, as I restart it, too, myself, 10x more than it actually crashes to prevent it from crashing.

I have Mavericks loaded on an external drive, and have tested that OS as well. It crashes hopelessly, just like Mountain Lion does.

I am at my wit's end and extremely frustrated, as I do not see a solution in sight, plus I cannot afford to buy a new computer.