Red and green square dots?

You're correct TheDoctorG. I am now able to offer yet another confirmation that baking does resolve the issue. Thanks to Richlove and all the others for taking the time to post their experiences and results.

For those of your who think that being insistent, polite or whatever to get your cards replaced are just spinning your wheels unfortunately. As others have repeatedly pointed out, those replacement cards have the same issue and will ultimately show up again with the "new" cards which in reality have been sitting in a warehouse somewhere for 3, 4 or 5 years.

I am a Mac guy now, and have been since 2003. Prior to that, I built my own PC's and I am an IT Network administrator by trade. I don't work on Mac's in a business environment, so I didn't have the suction cups and to be completely honest, I had never even seen the inside of my own 2010 27" iMac until yesterday. Not sure why, but I was actually nervous to do this, and I put it off and stayed on Mavericks as I too had horrible results trying to upgrade to Yosemite. My iMac works great in every other respect, and I felt I was forced in to going ahead with the bake simply because I wasn't going to waste money on a repair that I knew wouldn't ultimately fix it, I couldn't sell it in good conscience, and I couldn't throw it away and buy a new one knowing that the problem was actually so minor.

I ordered the cups from iFixIt, and went ahead and grabbed a new set of the tools while I was there. I very cautiously took my iMac apart following the instructions posted in this thread previously. Baked at 400 for just over 6 and a half minutes (oven was preheated). Once the card had fully cooled, I applied fresh heat sink compound and put it back together. It struck me on the re-assembly that it really isn't all that different from taking apart any computer, but for some reason, the Mac's just had this mysticism in my mind which made me nervous. I cannot explain why that was the case, it just was. Booted up, no issues! Upgraded to Yosemite, no issues. Ran for 24 hours, still no issues, with power saving back on and using it as I normally would for both low stress and high stress activities (like games).

I cannot recommend this for anyone who is not VERY comfortable with working inside a computer. For those folks, I know you're frustrated, but rather than going to Apple, who unless they install ovens at the Genius Bar is actually unable to permanently resolve the problem. Find a local computer store who will work on Macs. Show them this thread and ask if they are willing to do the work. A lot of those folks have probably heard of the baking method as it's not a new procedure for fixing this kind of issue with circuit boards. Even if they won't do the bake at the local store, they may be willing to remove your card and reinstall after you do the bake yourself.

5 days, still no issues, Bake-it!

Two weeks now and the spots came back.

I was watching a flash movie in Firefox and the vents of the CPU started spinning loudly, two minutes later the first squares reappeared. Flash in full screen grilled my GPU!! I'll send you a bill Adobe grrrr

Really? Correct me if I am wrong, but I think you are the first to have failure after baking. Is the problem the same as before or different? I think we baked around the same time, and I am still doing well.

The problem just started and has occurred twice in 10 hours and seems smaal at this moment. And it started with flash overheating mu GPU

Hello everyone,

We have two Imac 2010 mid with the same issu as everyone. As we knowledge apple doesn't respond to the problem. WE did send one imac to get check and apple said that everything was fine but the problem persist. I think it is time to take a lawsuit again the problem for the price we paid for our machine.

By the way we did the apple hardware test the long one and no problems came out. We do think that the problem is more software than hardware.

I've had this problem since december 2013, it's only getting worse. Next week I'm going to my Apple Service Provider to exchange the graphics card. I'm tired of this ****.

Well, it took 7 months after baking, but my dots finally came back.

I'm going to try round two of baking in a couple of weeks and will report back.

Cheers!

After much lurking, I'm about to bake my HD4850 following richlove's method (many thanks btw!). Just a couple of questiions:

- Should the card be placed with the chips up or down? (There does not seem to be a consensus about it)

- Some of the white puffy stuff remained on the memory modules after removing the heatsink. Should I remove the stuff before baking? If so, what product should I use to replace it?

Thanks!

I have a 2011 27 inch iMac with the same problem. I called the apple store and he had me do a key combination to reset the video on boot up.

He said the community was crazy for baking the video card and they will replace the video card at my expense if that didn't work.

He can thinks what he wants. All due respect but at the end of the day he's a step up from the best buy geek squad guys. And that's ok. There is actual science happening here, and this does work. This is not something unique to Apple. And infant these ATI Radon cards had similar issues in non-apple products.

Apple will replace the card at your cost. Ofcourse they will. But if you didn't have to pay apple to do it wouldn't you be better off? You can buy working graphics cards on eBay too. This is a last ditch effort before doing that.

I Got Apple to replace the card, as others have, and paid them to do it. That card simply went bad shortly after a period of time.

SInce the card is a Radeon, but uniquse to the iMac, it's not that easy to find, and I found cheaper to buy from Apple.

All that said, baking is the only thing that seems to work reliably, including getting Apple to replace it.

Cheers!

Here's a temporary fix that appears to work. I noticed that the dots show up big time when my imac goes into extended sleep mode. I would log in start working and within 2- 3 minutes everything would lock up forcing me to do a hard reboot and then everything would be fine or workable until the next time.

Suspecting it had something to do with automatic sleep mode - I now shut down running programs and then manually put the machine into sleep mode before I retire for the night. In the morning I usually have no issues as long as I stick to the routine and don't let it stay unused for any extended period of time which I am guessing is more than 2 or 3 hours.

Hope this helps as an alternative to baking.

The reason this happens is cooling. As the GPU cools very small gaps form in the solder. When it heats up it the solder expands and makes the gaps smaller. Baking reflows this and should re-fill the gaps. This will get progressively worse.

Hello all. I didn't scroll through all the pages of this thread, so perhaps the following detail has already been mentioned:

I mostly run using Win7 bootcamp on my Mid 2010 27" Mac. Recently, I switched to Yosemite 10.10.2 as the primary OS over Win7, and the screen problems appeared in force. When I go back to Win7, even for for a week or more, the problem goes away entirely. I don't have a single display issue while running Win7, and now I get constant display issues when running 10.10.2. There must be something in the way Windows uses the graphics card power management (either very efficiently, or very inefficiently) that keeps the problem from surfacing.

It's too bad, because I prefer the Mac interface, but it sound like short of baking the Graphics card, I may have to revert back to Win7 if things get worse.