Q: Red and green square dots?

Ratsandwich, I don't know.

I posted the process I found on youtube and it worked for me.

Not 100% (I still have sometimes some ghosty squares on my screen) but my iMac is working.

Well Zatlap, you are wrong. Let us all know when you've fixed the software.  Whatever software that is. Sorry dude it's not a patch fix.

Also if you're curious and if you want to know why the Newer OSXs cause more dots then think about how they are probably using more of the GPU resources and it heats up more. More animated (smooth animated genie effect ********) crap and more dependence on video in everyday use. Most of you are using these for graphics work so editing graphics and video uses which part of the computer? GPU. Sweet pic, exactly like the others I imagine. Eventually it will gink and freeze.

Doc, Absolutely Correct. short = resistance = Heat. Replace or reflow and up the cooling like with SMC or HDD fancontrol or similar.

Mike, You have to reflow or replace the GPU before you can cool it to keep the problem from occurring. After the dots appear it's borked.  But you are absolutely correct also, SMC fancontrol is probably the best solution to prevent this.

Again see my post at the top of page 38 (ungh), this is solved. Thread should be closed. like 400 posts? Shame. I cannot believe this even appears debatable.

That came off as really mean.  I'm sorry.  I was trying to edit that.

Zatlap wrote:

 

Anyway, I'd think twice before baking anything in the oven.

As well you should do, when baking it's easy to get it wrong and end up with an inedible mess - or even worse, burn something and set off the smoke alarm.

But seriously: I would be very surprised if changing the permissions on the root directory of your drive would actually fix a graphics problem.

Ratsandwich wrote:

 

You are all right and wrong.

 

You are all lucky I will waste some time to settle this.

 

None of you know how things work, this is why the thread is hundreds of posts long, for a Thermal Failure Issue.

 

The graphics cards are failing due to inadequate cooling. This is not due to Radeon or AMDs designs it is the heatsink that is directly responsible.

 

It's not a heat problem. My GPU wasn't running hot when it started failing, and it is running at the same temperatures after baking.

By the way, mine is still working perfectly, as in a full 100% absence of problems since the oven treatment.

So I purchased a new graphics card for my 2011 21.5 in 2.7 GHz imac. The card came with the heat sink connected to it. I followed directions to the letter to replace it (ifixit.com). The imac does not power on now. Checked everything twice, even reinstalled the old graphics card and nothing. when I push the power button on the back of the imac nothing happens, no optical drive or hard drive movement, nothing. I checked the AC cable coming into the power supply and I have voltage. I am at a loss! Does anybody have any help they could offer?

It could be a bad card.  Have you attempted to go back to the original?

Yes, I stated that in my post.

After a google search about my issue is has been suggested that the logic board went bad. I don't see how that could have happened? My other dilemma is that the computer has all my info on the hard drive so I cannot just give it to somebody to repair. I don't know what to do at this point?

There may be something inside shorting out or not connecting.  You can always mount a drive externally.  I'd check to make sure no connections are loose. Never ran into thisissue though.

Can’t mount to external drive when imac will not power on.

They sell USB connectors for SATA drives.  They're a few dollars on amazon.com.

Are you messing with me? All 3 of your replies are questions that I have already stated in my post!

Stated: “Checked everything twice, even reinstalled the old graphics card and nothing.“

Your Answer: “It could be a bad card.  Have you attempted to go back to the original?

Stated: “When I push the power button on the back of the imac nothing happens.”

You: “You can always mount a drive externally. “

Me: “Can’t mount to external drive when imac will not power on.“

You: “They sell USB connectors for SATA drives.  They're a few dollars on amazon.com.“

No. You stated you had a concern on getting your data.  I'm telling you how to do it. (ON a different computer).

That said, somewhere along the process of pulling you're card you've either left something disconnected or you shorted it out.  Taking the HD out may be the only way to recover what you need, without a logic board replacement.

You may have to contact an authorized Apple service provider and pay to have a full

diagnostic test sequence run on the computer in question. The problem may be involved

& require a new logic board or other components; that may totally cost more than you'd like.

• Find an Apple Authorized Service Provider

Sorry to not have an exacting answer for you to try; as I'm subscribed to this thread, I still

see replies even though the topic began in 2012 and not all of the content is relevant.

Good luck...!