iMac mid 2010 graphics issues after installing Yosemite

My iMac is identical to these specs, including the custom 12GB RAM config. Ever since installing Yosemite I'm experiencing stuttering / fps dropping as well. It's noticeable even in animation effects of opening a folder on the dock but even more obvious when playing XCOM: Enemy Unknown, a fairly old game, which should really not tax the system too much. Game almost comes to a crawl, even in basic menu screens. Oddly the problem only occurs after Mac has been on for some time... Not when I first login to my iMac after a restart.

Did anyone find a fix for this issue yet? S1000r, did you get your iMac fixed from the Apple Store?

I'm in the same boat. Same configuration, same simptoms. After a reboot (before the 1st sleep) Mac runs like a thunder (GUI, OS, games etc). As soon a I leave it in sleep a bit longer (more then a few hours) and wake it up I can notice the lag. PRAM reset didnt help, Only a reboot. This is def a Yosemite OS problem, because I had no problem (ever) with Mavericks.

I only use sleep option, so I'm not 2 happy with turning on/off my Mac 3-4 time a day. Will have to wait for a fix, in the mean time I'll turn it off every night and change the power options to not alow computer to go to sleep (apart from the screen).

Hope they patch this soon.

Would like to just add, that I have just woke up my Mac from sleep (entered it when I wrote the last post) and its working fine. So no reboot. I have had situations like this a few times in the last few days. Instant sleep and wake up does not reset the lag. Only this longer sleep sessions sometimes 'reset' the problem.

I too am having the same problem.

Here's what worked for me...

I log out before sleep. Yup, that's it!

I've had the same issues described above, on the same iMac version, but without the colour artefacts, and it's been driving me mad having to restart every time I want to use my iMac. I had tried everything: Repairing permissions in safe boot, SMC resets, PRAM resets - all to no avail. So, I thought I'd try logging out before sleep and it wakes up fine now!

In System Preferences - Security and Privacy - Advanced, I've set log out when idle to 20mins, with system sleep set to 21 mins in Energy Saver. Screen saver and display sleep are at 5 & 6mins.

Now my mac sleeps fine. On wake up I wait at the account selection screen for a minute or so for time machine to do its stuff and the disk to stop churning, then log in. Everything is fine, no stuttering viewing folders in the dock and games play without fps loss (I play World of Warcraft and Diablo3).

Thank you for posting this. I will def try this today and see what happens within a few days. Will post back.

This didnt work for me. Will give it a go a few more times but 1st try didnt help

I picked mine up from the Genius bar, they only reinstalled Yosemite didn't change any parts. I took it back home, booted, and the same problem appeared. I brought it back there and they will do more checks. Lots of wasted time...

They just called me, wanted >200 bucks for installing a new graphics card. I don't want to invest in the old machine so I told them to install Mavericks and test again. I can live with the old OS

It's not a graphics card issue - it has to be a software or driver issue - the number of people with this specific hardware setup that are experiencing it strongly supports that. That means it has to be fixable in Yosemite by an update at some point - I'll be surprised (and very disappointed) if it isn't. I definitely wouldn't pay them for a new graphics card.

I've raised this as an issue via the Apple Developer channel and sent them some diagnostics. Haven't heard anything else back (but that's normal until a fix is released anyway).

They installed Mavericks and the problem magically disappeared and my >$200 did not leave my wallet. Still they claim to be a graphics card hardware issue, although I tried to convince them it's a Yosemite driver. Anyways, let's hope for the Yosemite fix, any way to report this to Apple?

I have the same issue. I am running Mac book Pro 13 inch, Mid 2010 2.66Hgz Intel Core 2 Duo with 8GB of memory. I have over 200GB of space available and I have my machine connected to a MAC 27inch cinema screen. Since updating to Yosemite when I open more than 2 applications my laptop screen experiences graphics issues so bad I cannot see any images on the screen other than blocky image interference. I performed a clean install for yet another issue with Yosemite and while I am willing to put up with this issue, it would be nice to have this issue fixed sooner than later.

My concern is we will not get a fix for this until another OS X major release as was the case previously with people that had the same issue several releases back. For them Mavericks fixed the issue.

I have an iMac mid 2010 21.5" and the day after a yosemite install the screen suddenly went completely fuzzy with a multicoloured "Noise" and was unusable. in recovery it boots up ok but there are vertical bars across the entire screen.

i restarted in safe mode and got a graphics card fault message and reported it to apple.

up until the yosemite update the mac has been fine and dandy for nearly 4 years

spoke to apple support and had a lot of help. taking it to an approved repair shop where it will get a diagnostic check to see if the Graphics card is at fault and hopefully change it free of charge under consumer law. so im holding out a bit of hope to get this back up and working without getting slapped with a hefty repair bill. watch this space