iMac mid 2010 graphics issues after installing Yosemite

I've managed to get the Power Button trick to work (hurrah!), but *only* if I also use the Power Button to send the iMac to sleep. (You know - press Power, dialogue pops up, choose 'Sleep'). If I send the iMac to sleep using the keyboard shortcut (CMD-ALT-EJECT), then even the Power Button won't fix the graphics on wake.

For me, wake up with power button works even if I have put mac to sleep via keyboard shortcut

I'll keep trying then - maybe something I'm doing wrong. Either way, I have a solution to sleep and then wake the Mac and fix the graphics delay, so I'm mostly satisfied!

I though Leap Motion (little hand) out of the menu bar and next second the blocks are gone.

Transparency OFF did the trick for me.

Running iMac 27 mid 2011 12,2 Radeon 6770M 512

...if anyone braves the 10.10.1 bleeding edge with any success I am all ears with many thanks...

I just went through the 'upgrade' to yose only to need to 'downgrade' to the mavericks that almost works as well as snow so far...

iCloud and Yose upgrade notices feel like popup spam to me?

Not why I was on apple from System 6...

Perhaps I am missing why apple is so persistent - data mining & ad revenues?

I have the same system as kmdriver, a mid-2010 iMac 27", 2,93 GHz Intel Core i7, ATI Radeon HD 5750 1GB and are also affected by this issue.

My observations:

1. The issue STILL occurs with Yosemite 10.10.1 😠
2. It is not related to the transparency setting. Disabling it makes no difference.
3. It is not related to PRAM (tried that, no difference)
4. It is not related to upgrading vs new install (tried that, no difference)
5. The problem occurs after waking the iMac up from (deep or long enough) sleep and is only temporarily "fixable" by rebooting.
6. It seems that 3d graphics acceleration gets totally disabled when this occurs and mac os resorts to software rendering. Cinebench R15 score goes from 52 fps to 14 fps when the issue occurs.

This is annoying as **** and really makes Yosemite a pain to use on this machine. Using Exposé is a laggy joke.

I can't understand how Apple could NOT FIX THIS with the 10.10.1 update. How can we bring this to their attention?

It is indeed disappointing that the problem is not addressed in 10.10.1.

However - there is a 'work-around' as discussed in this thread and elsewhere - which is to use the Power Button to wake the iMac from sleep instead of the keyboard. You have to:

1/ Ensure the iMac has 'fully' gone to sleep. When a Mac first goes into sleep mode the screen switches off and often the fans will stop, but some additional processing continues (writing memory to disk, amongst others - this can take some time especially if you have a lot of RAM - it's a couple of minutes on my iMac). Once the additional processing is done there is a faintly audible 'clunk' type sound from within the iMac case (and if your hard disk is not an SSD you may be able to hear that spin down also. This is the kind of sound you would associate with most mains-powered electronic devices powering down - your TV might make a similar sort of noise. Anyway - once that has happened (almost always within 5 minutes, usually quicker):

2/ Use the power button to wake the mac. Most users with the graphics problem report that using the power button once full sleep is entered fixes it.

Hi. First post here.

I can confirm power button work-around working here for me. Tried after a full night of sleep mode (the computer, not me...).

• Mid 2010 27" iMac with 10.10.1.
• Optical drive replaced with SSD, on a caddy, for OS X.
• SSD (sticked inside besides main HD) + mechanical HD in Fusion drive mode for data.
• After-market memory upgrade to 12 Gb.

By the way, I'm doing the tests with Unigine Heaven Benchmark. In "problem mode" it struggles just above 8 frames per second. In "normal working mode" soars up to 35-40 frames per second. For me, an easy way to check if I'm in "problem mode" or not.

I get no artifacts, just slow graphic performance.

Thanks to all for your information.

10.10.1 did NOT fix the issue, still the same behaviour.

I tried the workaround to wake the iMac with the power button which seems to work. But I figured out, that it also works with the space key from the keyboard. In fact it doesn't matter how you wake the iMac. The graphics issues seem to occur only, if the iMac was asleep for quite a long time (some hours). But if the iMac was in standby for some minutes everything works after waking it up (with power button OR space key).

At least, these are my findings.

reporting back with my graphics issue. my imac has had a graphics card replacement free of charge under consumer law. got a phone call this morning to collect it from the repair shop. couldnt be happier. well done apple.

Same iMac config here, paid the $200 to replace my ATI card that was demonstrating the screen "noise/blocky pixel" issue that others have seen. However, I saw that issue before 10.10.

Currently running 10.10.1 with a replaced video card, have the same noise issue, periodically the iMac will freeze and upon reboot will tell me there was a graphics issue.

I also see the graphics lag problem, both within finder and when playing World of Warcraft that seems to not happen if I do not allow the iMac to go to sleep. Have not yet tried the power button wake method.

So for me...two distinct issues...laggy graphics performance when returning from sleep (mitigated by not letting the iMac go to sleep) and blocky/noisy pixels that ultimately result in a lock up and a reboot ALL AFTER A REPLACED VIDEO CARD.

I was waiting for someone to have this issue. I am sorry you are the one to discover it but I have suspected the graphics issue was a software bug from the beginning.

Patrick S.

What is interesting is that my experience, screenshots, hangs, laggy graphics and all, closely match the experiences that have been posted in this thread. However, with the exception of the laggy graphics, my video corruption and hangs started BEFORE Yosemite and possibly even before Mavericks (though I can't recall now for certain.)

I'm a big World of Warcraft player here and I had attributed the original issue to overheating the video card from excessive playing causing it to fail. But now, given what you all are posting, I'm starting to wonder if it's software or hardware. Very difficult issue and I don't have any of the hardware test utilities to run against the machine.