Q: Mid 2011 iMac Graphics Problems with Yosemite

About a week now without problems.  No pixel confetti, kernel panics, or app crashes.

My problem is the same pixelation but also Raw files loading black or partly black in the thumbnails only. Photos are there when I open.

Here's my 2009 imac - same problem. Took it in to Apple checked out chip/board that's OK. Said it was software. Erased hard drive and started new and problem is back.

Thanks !  This actually solved my problem ... The display was taking a long time to refresh when switching windows and in particular when activating Mission Control.

The Mac is noticeably quicker to run too

I have a mid 2010 iMac 27 ..

2.8 GHz Intel Core i5

4 GB 1333 MHz DDR3

1TB

ATI Radeon HD 5750 1024 MB

YOSEMITE 10.10.1 (14B25)

. For about a year i have had this problem of blinking green and purple squares all over the screen. Sometimes a stain next to the cursor, and sometimes a crash. I have had 3 crashes in the last month and this issue is much worse with the Yosemite, but it has been present since Mavericks

. What i can say about MY experience, is that this issue only happens when the iMac is cold, yes as crazy as this sounds, once the iMac's temperature rises, the issue stops. And i can use it as always.

Thats why i came to the conclusion it cannot be software related. It has to be hardware. Yes transparency disabling may help, but thats just a temporary solution, and btw, you are suposed to be able to use and experience this features.

Then why is it worse with YOSEMITE?? well, Yosemite simply squeezes the Video card power even further, and of course, as it is damaged, it can't handle it.

I thinks the only solution, REAL SOLUTION, will be changing the Video card.

Sory for my English =S

K_Rek

Some New Refers To Our Problem? Any solution?

Just started following this

I have a mid or early 2011 21.5" imac, upgraded to yosemite a couple weeks ago

I have the same problems that appear prevalent on these posts. Could not run hardware test, kept restarting holding down D, nothing. Used recovery, just erased the disk and reloaded lion, now nothing

just a solid light gray screen

utterly lost

I have at least 2 kernel panics a week, and other issues sometimes error other day that involve rebooting the computer.

The latest thing--

I cannot access websites other than Google or Facebook (maybe others) until after I reboot the computer. I have top of the line virus protection with real-time protection enabled so it can't be that. It isn't limited to browsers it is literally at the network level. pings fail.

I am just really fed up with the issues. So many issues with iOS 8 as well that make the iPhone almost unusable, and this is the 6 Plus.

first shut off your anti virus they cause more trouble and issues then they are worth. if you are running a program like mac cleaner get rid of it as that program is maleware very bad for your computer. It appears i find a pattern here no one shuts there computer off. I have no issues same computer but mine is from Dec 2011 no issues at all with 10.10 but i do not run any of the junk adware like mac cleaner or any anti virus programs last anti virus program i ran it trashed my macbook pro to the point i had to do a clean install. I shut my mac down every night and rarely leave it on more then 24 hours unless i am doing a video project. Issue is the iMac is getting to hot and is not let time to cool down when not in use causing the graphics card to over heat then fail. From what i gather apple is away of the issue and there will be a graphics card update in the next OS update to fix some of the issue. There might even be a firmware update to fix this as well. Only issue with viruses i am aware is male and add ware that is user installed.

"I have top of the line virus protection with real-time protection enabled so it can't be that. It isn't limited to browsers it is literally at the network level. pings fail." uninstall the anti virus program most of your problem with kernel panics will go away anti virus software are sales gimmick utterly useless for macs.

Executing this command on Terminal has solved everything on mi iMac.

sudo nvram boot-args="debug=0x10"

Hello K_Rek , fast You gotta Have Solution To Your Problem? My problem is exactly the same as yours, my machine is identical to yours.

My problem was only solved after I stopped using Safari and I started using Google Chorme . I'm 99 % sure that the problem is with Safari . Has two days left the Apple browser and now everything is as it should be .

For those of you with 27" 2011-2012 iMacs with AMD Radeon HD 6970M video cards that are having trouble, here's some good news for you

There's a major problem with them so Apple will replace it for FREE. Even better, I spoke to an Apple tech who said they probably that model isn't being manufactured any more so you'll more than likely get a free upgrade to a more advanced, modern video card with more memory.

You have 4 years from the first retail sale date of your iMac. (I have until next year.)

Here's the official link:

iMac (27-inch): AMD Radeon 6970M Video Card Replacement Program - Apple Support

It's not. My problems started when using Chrome.

We're just going to have to wait for the next OS update, it looks like.