Q: Red and green square dots?

Paid Apple Support  to replace my graphics card  iMac, 27-Inch, Late 2009.   Graphics ATI Radeon HD 4850 512 MB RAM

Seems to have fixed the problem.   

I did not try the Engery Saving savings seettings like others.  I am using the defaults.

Having same issue the past few weeks with my late 2009 model. How much was the graphics card repair? Since it seems that might be my only option.

Several in this thread have had their GPUs replaced and it did not fix the problem. I'm not saying you shouldn't do it, just saying that there is a chance you'll pay and it won't repair the issue. Many of us believe this is NOT a hardware problem but one with software.

I had my graphics card replaced at the beginning of April by a local shop that is an authorized Apple repair center. Cost was $432.40. It has resolved my issue so far. The card tested OK when they used the Apple diagnostics, but it the anomalies were obvious to observe in spite of that. The technician seemed quite confident that the new graphics card would resolve the problem and, so far anyway, it has.

Good luck with yours!

Apple Store charged me $248.32 including tax and labor to replace ATI Radeon HD 4850 512 MB RAM. 

It took about 5 days.  One day just for a burn in test by Apple to be sure it resolved the issue even under heavy load and when parts were heated up. 

So far seems to have fixed things for me.

So I've been running with all my energy saving setting turned off since the 21st and so far so good. This is the longest I've gone without any artifacts or my system locking up. Not an ideal solution but it's the only thing that has worked so far. We will see how long it holds up.

I'm still not convinced that it's a hardware problem. Just doesn't make sense to me that preventing the system from going into sleep mode fixes the issue. If it were the GPU, it would make more sense that this would make the issue worse. Maybe we have the same symptoms but two different root causes. One is hardware and the other is ???

My money's on video card firmware problems.

"One is hardware and the other is ???"

Not exactly.

It's "both".

I've seen pure GPU related heat artifacts, and these aren't them. Neither do they appear to be pure software either. The only users that have had full resolution of the problem are the ones that changed hardware (some, but not all, as you previously pointed out). Some users can maintain (for now, at least) an artifact free system by setting certain software parameters.

These artifacts present themselves reliably when particular hardware conditions are met- but we don't know which ones exactly. Also, these conditions may be mitigated by parameters in the software- as some users have discovered. 

Given that we can't determine what conditions bring about the artifacts, I think it's a little unreasonable to expect the Apple guys or the ATI guys to run out and start debugging errata that seems to occur only on failing hardware.

It does involve hardware. We can say that with 100% certainty.

But as I pointed out earlier, there is more to the hardware than the GPU card: it's heatsink, the heatsink mounting, the TIM, the motherboard connectors, and my fave- that 4 year old hearing aid battery that you trust to store the PRAM.

Take it apart (not hard, but you will spend all Saturday doing it), reflow the GPU, replace the TIM with some high quality pads, blow out the dust, and replace the battery. If it still fails, it's most likely a failing IC/GPU/RAM, or a bad heatsink. Upgrade to a new card that comes with it's own heatsink for your iMac model.

Rest assured, there is a limit to the number of things that can go wrong. Just go about addressing them in a methodical fashion and you will fix it.

R

The real question is... if system usage is being sent to Apple when hardware fails or something crashes, why shouldn't we expect Apple to address the issue. I understand that they may never provide a solution here in the forum, but the data is available to them via error reports.

With so many people outside of these threads having the same issue, the error reports have to be piling up. I think a little digging is not much to ask of Apple and ATI. Why else would one opt in for system reports to be sent?

This is an issue that is not self imposed by the users... Translation, we didn't know we were purchasing lemons from Apple.

And that's a great question.

In your own business, don't you study your failures? I do.

And I expect Apple and ATI do as well. We've seen graphics card and hard drive recalls in the past, so we know they have a QC mechanism in place. I know of a number of times the Genius has replaced entire devices when it wasn't necessarily indicated, and have wondered if these weren't meant for study.

I think it may be a little different though when you're talking about products that are past the 3 years of AppleCare. If I understand correctly, electronics and their components age predictibly. They may I already know about this and aren't addressing it for that reason.

Also, this is one weird malfunction that seems to affect only a small number of people. It may be below radar. And, crash reports/hardware reports I think are unlikely to benefit in this situation, and the hardware report just isn't capable of giving the kind of info people think.

I must say I've owned many Apple products over the years, and any "Lemons" were replaced promptly at no charge. I still think their quality is far above all else in the field, but we all take our chances. The more time, the more likely something fails. Trust me- I'm currently running an overclocked MacPro1,1 that's lost it's Northbridge communication to the lower RAM riser. But look at what I just said.... I've lost half my Northbridge on an 8 year old MacPro, and I'm still using it. That speaks to quality in my book.

Great news, everyone! After things getting so bad that my iMac would crash many times per day a month ago, after a bit of effort, today my iMac has an uptime of 30 days!

If you can dedicate a few hours opening your computer and removing the graphics card, that might just be enough to put all this trouble beind you. Read on...

As you know I have been in here since the beginning. Well over a year of annoying colored dots/blotches/whatever was annoying, then the crashing gradually started about six months ago. I lived with Quartz Extreme disabled for months, which did help. But it kept getting worse.

Month by month, week by week, I could see things get worse, with more graphics corruption, then hard crashes first weekly, then gradually daily, and two months ago it got to the point that every time I sat at my computer, it would crash within minutes.

Inspired by those who mentioned reflowing their graphics card, I found a satuday that I had several hours to dedicate, and carefully followed instructions to open up my iMac and get the graphics card out. I also ordered new thermal paste.

Let me first say that though I removed my motherboard, I later realized it is not needed. The 5750 can be removed with much less effort and fragile cable removal by removing its few securing screws and its one temperature cable, then lifted straight up and out.

After removing the heatsink and cleaning off all thermal compound, I decided NOT to reflow, there are just too many tiny comonents and those upside-down pose a chance of falling off. Instead I warmed it well with a heat gun, then applied new thermal compound and re-assembled everything. I also was sure to clean all contacts with alcohol.

That was 30 days ago and my iMac has been as good as new ever since. To my surprise I did not find much dust inside, that was not the issue. I am convinced there is a deteriorating connection, weather it be contacts between the graphics card and the motherboard, or solder cracks on the graphics card, both of which are worsened when cold. No doubt there is some relation to low-level software or graphics drivers that do not handle the problem well, perhaps when they do not get the response they are expecting and the computer freezes. It also seems there is clearly a batch issue with this card, and some getting replacement cards also get another with the same eventual problem.

Seriously though I wish I had attempted this months sooner. A few hours and my nearly junk iMac was new again.

Thanks for sharing your success story, Josh!

So far, merely defeating all energy-saving settings has left me "faultless" for several months - but your procedure will most likely be my first recourse, should additional problems arise...

Josh,

**** GLAD to hear that!

I feel like folks are just a bit afraid to open up their iMac and try, and I hope your story will help others gain the nerve and take the plunge.

Best of luck pal. I'll be keeping my fingers crossed with you.

R

I did pretty much the opposite. I removed reminance of legacy programs and turned all my energy saving utilities onl (to avoid over heating) to obtain the same success.

jmf

I got the answer months ago and even posted it on this board when I decided to take it in to be fixed. First replaced Apple graphics card then that got fried. Second time replace graphic card and logic board its been no problems since March 7 2014.

I lucked out also because the first time they got it wrong and didn't charge me for the 2nd repair logic board, graphics card or memory.