Q: Imac display issues following Yosemite upgrade

Thank you. I did see that article a few weeks back and contacted Apple Care but my video card was a slightly different model and not part of the recall unfortunately.

Same here. My hardware  is

iMac 27-inch, Mid 2010

Processor  2.93 GHz Intel Core i7

Graphics  ATI Radeon HD 5750 1024 MB

I think I will install a clean Yosemite on an external drive, and cart my iMac to the Apple Store.  My screen glitches are fairly extreme and hard to ignore.

Good luck. I called Apple and found out that although my iMac is from the right timeframe and it exhibits all the symptoms of the graphics card problem, it doesn't have the serial number series that Apple will repair for free, so I'm stuck paying for a new card. There has already been a hard drive recall on my machine, which I chose not to replace.

None one of this makes me feel real good about Apple.

The fix is to disable transparency.  I did it on 3 different computers now and it worked like a charm on all.

Been there, done that. Doesn't work.

Here's a photo taken with my iPhone.

Bingo.  That's the problem.

My experience:

Occasional flicker in Mountain Lion.  Even less flicker in Mavericks... Yosemite: Unusable due to continuous flicker and eventual freeze up. 

Software Fix:

Since many of us have the exact same problem:  this is not a hardware issue. It is an Apple Yosemite conformance problem.  Apple did not test Yosemite or did not choose to fix issues with the legacy hardware that many of us still use on a daily basis.  Mountain Lion and Mavericks show that this hardware can be made to function properly.

It is now Apple's choice: Fix this software conformance problem and or leave a significant number of otherwise happy customers stranded.

Personally, I think Apple will choose the former and fix the problem but only when they have an understanding of the number of customers involved.  The onus is therefore on each of us to raise the issue with Apple either by email, phone or through the Apple store.

Until we get an answer, Yosemite is not an option for my iMac.

-- Sent from my completely functional 2010 MacBook Air running Yosemite.

Although this is a software issue and Apple should fix it, I don't think it's fair to say that Apple "didn't test" (disclaimer, I am a software e engineer and testing is very very hard). This is also because a very minority of people have this issue.

I do hope apple with fix it though.

On the bright side, I haven't see this issue already after my last reboot and I have everything as default. Last reboot was already last week? I cannot remember...

I have the exact same issue everyone describes here, would be very nice if apple fixed it in an upgrade.  I have a 27" iMac - (mid 2010 model).  When Mavericks first came out I experienced this exact same issue and after a couple patch cycles it was fixed.  I'm hopeful, but do find it super annoying.  This upgrade is also very unstable, reminds me of my Mac circa 1997 that would freeze up all the time.  Hopefully the constant stream of auto-reported graphics card issues will get Apple going on a fix

Exactly the same problem on MacBook Pro (Early 2011), running 10.10.1. Randomly goes away, but is even more problematic when plugging into and out of a Thunderbolt display.

Here's what I have done so far, short of paying $350 for a new graphics card:

1. Uninstalled all old versions of Adobe Creative Suite products.
2. Uninstalled old software I no longer use.
3. Updated online backup software.
4. Disabled Parallels Access.
5. Disabled Dashboard.
6. Disabled the Spaces feature.
7. Changed my screensaver from the default to one that displays one image at a time, instead of shuffling multiple images. I also turned off the time display on the screensaver.

I know some people have had success with the transparency setting, but I have not.

No. 6 and 7 was something I just tried. Previous to that, the problem didn't happen as often, but still occurred. I'm hopeful about the last two and will report back.

A new video card in my 2011 iMac cost $151+tax including labor from the Apple Store. Good luck.

While not free, $151 is reasonable and less than the cost of Apple Care.

Same issue - pixilation - increased following upgrade to Yosemite. 

The most recent episode required a hard reboot.  Ouch!

iMac 27"

Thanks for the comments.  Hope Apple fixes this.  Must be a software issue (note the increased incidence following Yosemite).

I will try turning transparency off.

For those have screen issues with the mid 2010 iMac and ATI card: 

How did you install Yosemite?

1. Installed over Mavericks or earlier version of OS X keeping apps and data.

  or

2.  Created / erased partition and installed a completely fresh version of Yosemite.

In preparation for taking my iMac to an Apple store, I formatted a new partition and installed clean copy of Yosemite from USB to "prove" that Yosemite is the culprit. Only problem: So far, no screen glitches.  Before I continue adding more apps to this Yosemite instance, has anyone else had success with a clean install? 

Like many of you I am sure, I run screen intensive / retina apps including Final Cut Pro and Photoshop. They are not yet installed and may indeed be part of the equation.  Has anyone had a clean Yosemite with no extra apps, perform better?