iMac mid 2010 graphics issues after installing Yosemite

In response to Jas's post, I was also experiencing some strange side effects when upgrading to Yosemite. My issues included random crashes (that restarted the iMac) when the computer was idling and full graphics crashes (that required a hard restart to fix) when playing any type of video file in many different video player softwares. I followed the link provided and after months of dealing with the problems and actively avoiding them (by not watching videos and shutting down any time I left the computer), I decided to give the downgrade/upgrade option a go.

This wasn't easy as my iMac was given to me by Apple as a replacement for an old 24" I had which broke and I was not given the official 'grey' discs that has the right OS for my 27" iMac mid 2010 (it flat out won't boot the standard Snow Leopard Disc, with the Snow Leopard picture on the front). These disc's cannot be obtained anywhere online and I was massively lucky that an old friend has the same model and could lend them to me. Side note: Now that all OS's are free, apple should provide all distro's of there various OS X versions, past and present, for free on their site.

Anyways, after downgrading to Snow Leopard and upgrading to Yosemite, I can confirm that I am no longer experiencing any issues with my iMac. I recommend this as an option for people who have exhausted all other options to fix their issues. I do worry however that every year I will have to repeat this process to upgrade to new versions of OS X. This isn't ideal as it requires a fresh format and all settings and applications have to be configured and installed before the computer is usable again. Either way I'm happy I have a working iMac again (after spending an arm and a leg in the first place).

Hope this post help's people like Jas's did for me.

It's simple as this, you have a faulty GPU or you don't. If you do, no voodoo will help. If you don't, you can install whatever OSX on your iMac and it will work as expected. Although, with Yosemite, you'll experience the sleep slowdown with ATI/AMD GPUs.

As a sidenote, you can boot Yosemite installer from internet with your iMac by holding down command-option-r on bootup.

I have a sneaking suspicion that this is a software problem that brings out a potential hardware problem. I am not a hardware expert, but I have done computer support at both the client level and enterprise level for the better part of the last 15 years. I am experienced when it comes to troubleshooting and I have seen similar issues in the past while working enterprise support for Dell. The issue doesn't manifest itself until you upgrade to Mavericks. That is likely where the software brings out a potential hardware flaw with what I am speculating is a problem with a certain manufacturing lot of the Graphic cards. Other people indicated that they have resolved the issues by replacing a mother board and/or a video card. The replacement likely fixes the issue because the newer hardware is a newer release of the hardware that likely has some modification that was done to the hardware to address this. The same could be true about a mother board. Manufactures do this all the time where they rework the hardware with a small modification to it due to potential issues that find in early release of the hardware. I have worked cases that have played out exactly like that... Why else would people only experience this issue when after they upgrade to mavericks???

The problems seem to be less likely to happen when you turn down the transparency in accessibility, but my computer will still freeze and crash from time to time. It is sad that this isn't fixed or that there isn't a program to replace the potentially faulty hardware. Again this is somewhat speculation, but it is the only thing that would make sense to me for this issue without having access to the privileged information that Apple Support dose...

Well... It looks like they haver "hard fixed" this bug on El Capitán... Now, no matter how hard or long I bang on my keyboard or sweep the whole house with my mouse, the **** computer will NOT wake up from sleep... I have to press the power button to wake her up. I even tried to sit on the keyboard: nothing 😁

This is hilarious...

By the way, I do recommend an upgrade to 10.11. IT IS QUITE FASTER.

I'm running Ol' Captain now and I can sleep my iMac with option+cmd+eject and wake from mouse / keyboard without entering 'crap graphics mode'. 🙂

I don't remember this from Yosemite, could be a new setting, in Bluetooth > Advanced:

This might provide a better way to wake your mac than sitting on the keyboard!

Now I know to what extend my wife's t-shirt reading "I'm with stupid ->" is right.

Thanks a lot for pointing out the new setting for Bluetooth. I can stop sitting on the keyboard now.

Seriously: everything works fine now. Tested wake up with bluetooth and NOT showing the problem.

I think this is a hardware problem, in particular to the AMD's Radeon 5750 (a.k.a. Juniper). I have been running linux on my iMac mid 2010 for a few years. A few months ago, I started to experience the problem described in this blog page: flickering squares of red, green, yellow. At first I thought the problem was related the graphics driver in the Linux kernel, because the machine was working fine till this year. But no matter how much I tweaked the Linux OS, the problem didn't go away. So I booted into mac OS (still running ancient Mavericks). After a few minutes of usage, those flicking blobs showed up too. This is points to lousy quality control in the hardware. Some parts manifested problem early, some late. Probably Apple found a hot fix to mask the problem when the model was first released. Now majority of those iMac's are out of warranty, so they are home free. Probably Apple made the right decision to ditch AMD (ATI) and to go with NVIDIA ( as a side note, if you search for the software support of ATI display cards outside of Windows, you will find piles and piles of complaints. No wonder the company is going down the drain).