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I recently removed the ram from my iMac & replaced it with the stock 4gb sticks. I then did an internet restore (to lion), realized I could not upgrade direct to high Sierra, then used a boot ssd drive to install high Sierra (no migration). The problem still persists (but did not show up in lion.). I wouldn’t read to much into the failure for the problem to show up for the brief time in lion as it is a somewhat intermittent problem (and the computer was warmer.)

One of the reasons I did the scorched earth install attempt and changed out the ram is I have given up and purchased a new iMac.

I intend on posting a link on the for sale forum here soon to sell my 2011 iMac for parts, stating the known issues for any interested buyer.
 
I recently removed the ram from my iMac & replaced it with the stock 4gb sticks. I then did an internet restore (to lion), realized I could not upgrade direct to high Sierra, then used a boot ssd drive to install high Sierra (no migration). The problem still persists (but did not show up in lion.). I wouldn’t read to much into the failure for the problem to show up for the brief time in lion as it is a somewhat intermittent problem (and the computer was warmer.)

One of the reasons I did the scorched earth install attempt and changed out the ram is I have given up and purchased a new iMac.

I intend on posting a link on the for sale forum here soon to sell my 2011 iMac for parts, stating the known issues for any interested buyer.

Do you still have the original Mac OS X install disc that came with the computer? I think it was Snow Leopard 10.6.6 wasn't it? Now that you've migrated your data to your new machine, it'd be great if you could try a fresh install of an older OS version. I too have a 2011 iMac here working perfectly on 10.9.5 (Mavericks), I'm really hesitant to upgrade to anything else, especially after reading this thread. It'd really help us A LOT if we/you could show that it was software dependant or definitely hardware dependant. To me, it seems like High Sierra 'cooks' the GPU in some weird way beyond comprehension, that according to one other in the thread (jeffmazur, post #50) continues to show the 'cooked' defects even after reverting to an earlier OS. But that was just one guys experience, if you got time brother, I for one would really appreciate it if you could somehow try an earlier version. Thanks.
 
Imac 27" Mid 2011,
2.7 GHz i5,
20gb ddr3
AMD Radeon HD 6770M 512mb
512gb SSD OS + Original 1TB Seagate

Same graphics issues, this has been going on for a while now, but it would seem to be a driver issue rather than hardware. Up to 10.13.3 I could make it disappear by going full screen with any app, Safari is the worst culprit. The corruption also occurred on desktop, when waking after long periods of sleep. Opening an app and going full screen would clear it also.
10.13.4 Wake the machine to start the day and within 15minutes graphics issue and lock up. This issue is changing with the OS, somewhere in the middle of 10.12 this started. Will Apple fix it? or am I being encourage to buy a new one?
Reading your posts leads me to consider that the gpu rom was flashed somewhere along the line during the 10.12 era. Otherwise the issue would have disappeared as you delve back in time.
I don't remember this during 10.11 or previously.
 
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Imac 27" Mid 2011,
2.7 GHz i5,
20gb ddr3
AMD Radeon HD 6770M 512mb
512gb SSD OS + Original 1TB Seagate

Will Apple fix it?

Please see my post #41. The biggest issue I had with Apple support is that they claimed no one else had reported the problem. If enough of us complain PERHAPS they'll look into it.
 
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Thanks everyone for all the help on this long running thread. Last week I sold my 2011 iMac with the graphic issues to Gazelle, for $90 as a final price. (They paid the shipping, also there was no interest on the for sale forum here to buy it for parts.)

FYI: I was able to replicate the issue consistently by chilling the computer in a cold garage overnight, and able to reduce (but not eliminate) the issue by placing the computer in a warm room, or letting it run a few hours to warm the system up, so others with these issues may want to try to see if there issues come and go with temperature as well.
 
Thanks everyone for all the help on this long running thread. Last week I sold my 2011 iMac with the graphic issues to Gazelle, for $90 as a final price. (They paid the shipping, also there was no interest on the for sale forum here to buy it for parts.)

FYI: I was able to replicate the issue consistently by chilling the computer in a cold garage overnight, and able to reduce (but not eliminate) the issue by placing the computer in a warm room, or letting it run a few hours to warm the system up, so others with these issues may want to try to see if there issues come and go with temperature as well.


mines still doing it. It really is becoming annoying as F!!!!!!!!
 
Curious if anyone has access to Mojave and sees the issue persist.

I am still experiencing this and waiting on the new iMac hardware to be announced before buying the outdated 2017 model. I know. I could wait several months.
 
Curious if anyone has access to Mojave and sees the issue persist.

I am still experiencing this and waiting on the new iMac hardware to be announced before buying the outdated 2017 model. I know. I could wait several months.


Our 2011 Macs have reached end of life with Apple. They won’t support Mohave. I guess it’s time for me to just upgrade soon. F it. Tired of dealing with this issue.
 
FYI: I was able to replicate the issue consistently by chilling the computer in a cold garage overnight, and able to reduce (but not eliminate) the issue by placing the computer in a warm room, or letting it run a few hours to warm the system up, so others with these issues may want to try to see if there issues come and go with temperature as well.

Well, FWIW I have had a different experience. The issue was really bad on my machine, especially when using Safari or Firefox. Then the corruption would take over most of the screen in the Finder, etc. Bringing an app full screen or going in/out of sleep mode would always fix issue but only for a short time.

Then I left for a two week vacation with the iMac turned off. Came back and without doing anything else it is now 98% better. Been using it for several weeks - just the way I always do (computer stays on 24/7 but display sleeps after 10 minutes) - and only saw a hint of corruption a couple of times. Hope I haven't just jinxed it but go figure!
 
Well, FWIW I have had a different experience. The issue was really bad on my machine, especially when using Safari or Firefox. Then the corruption would take over most of the screen in the Finder, etc. Bringing an app full screen or going in/out of sleep mode would always fix issue but only for a short time.

Then I left for a two week vacation with the iMac turned off. Came back and without doing anything else it is now 98% better. Been using it for several weeks - just the way I always do (computer stays on 24/7 but display sleeps after 10 minutes) - and only saw a hint of corruption a couple of times. Hope I haven't just jinxed it but go figure!


My computer has become almost unusable. It is constantly locking up and the graphics issues still plague me. I wish they would update the mac lineup as they are dated. I need a new machine asap. It does really piss me off...this issue... that we all have the second High Sierra came out. Clearly whatever happened during that update it messed up our machines.
 
My computer has become almost unusable. It is constantly locking up and the graphics issues still plague me. I wish they would update the mac lineup as they are dated. I need a new machine asap. It does really piss me off...this issue... that we all have the second High Sierra came out. Clearly whatever happened during that update it messed up our machines.

I notice in Safe mode this issue completely goes away.
 
Well you were right. They replaced the HD, video card and display the issue remained. They wanted to replace the logic board but I declined since they offered me any PC for 50% off so I took it. Still have my IMac and did not get charge for the repairs. I did hear one tech say it may be an OS issue with our particular model however Apple will not patch a 2011 IMac.
[doublepost=1541198463][/doublepost]seems like the business plan there. create a problem and cost to fix it....its the OS upgrade that started my problem...have to reboot several times a day now....pathetic.....
 
mines still doing it. It really is becoming annoying as F!!!!!!!!


You have what is known in the repair business as thermal issue, with one electronic component. Most of the time in the audio/video field the culprit was a "cold solder Joint." The joint between the component and the board develops a crack, and with differences between hot and cold, the resulting thermal expansion and contraction, causes intermittent behavior.

What you do is, get a soft toothbrush, a hair dryer and a can of freeze spray. Allow the unit to get to where the issue is occurring, then begin brushing lightly every component on the board. If it acts up, stop and pinpoint it. If not, take the hairdryer and warm each area of the board. If you find the area, shoot freeze spray on it, and see if it returns to life. Components go thermal also, which is the likely scenario for your computer, solder rarely fails. Anyway, if it's something simple like a resistor or capacitor, you can replace one of those, and save yourself a couple hundred ducketts. Never hurts to try.

It may be software related or caused by, but it's manifesting itself in a thermal breakdown component issue. Find that component.

Then someone here could run a temp profile on 10.12.6, while you run one on 10.13.xxx. Evidence of a software or firmware upgrade issue.
 
My computer has become almost unusable. It is constantly locking up and the graphics issues still plague me. I wish they would update the mac lineup as they are dated. I need a new machine asap. It does really piss me off...this issue... that we all have the second High Sierra came out. Clearly whatever happened during that update it messed up our machines.

My computer also just got a lot worse; terrible display issues and crashes. SO I WAS DETERMINED TO COME UP WITH A WORKABLE SOLUTION. From everyone's agreement that the issue could be temporarily fixed by going full screen or safe booting, I figured it might be resolved by eliminating the Radeon driver from the System Library. You have to boot into the Recovery volume (hold Option while Restarting). Then you can launch Utilities/Terminal and rename the appropriate drivers so they won't load:

cd /Volumes/<YOUR DRIVE NAME>
mv /System/Library/Extensions/AMD6000Controller.kext disabledAMD6000
mv /System/Library/Extensions/AMDRadeonX3000.kext disabledAMDRadeonX3000

After doing this, Quit the Terminal, Quit mac OS Utilities, and Restart the computer. The display WILL BE A LITTLE SLOW AND FUNKY at times, but perfectly usable. AND NO MORE PIXELATION OR CRASHES!!!
 
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My computer also just got a lot worse; terrible display issues and crashes. SO I WAS DETERMINED TO COME UP WITH A WORKABLE SOLUTION. From everyone's agreement that the issue could be temporarily fixed by going full screen or safe booting, I figured it might be resolved by eliminating the Radeon driver from the System Library. You have to boot into the Restore volume (hold Option while Restarting). Then you can launch the Terminal and rename the appropriate drivers:

mv /System/Library/Extensions/AMD6000Controller.kext disabledAMD6000
mv /System/Library/Extensions/AMDRadeonX3000.kext disabledAMDRadeonX3000

After doing this, Quit the Terminal and Restart the computer. The display WILL BE A LITTLE SLOW AND FUNKY at times, but perfectly usable. AND NO MORE PIXELATION OR CRASHES!!!


Awesome workaround. I knew it was the driver. I wound up selling mine and bought a new Mac mini.
 
Awesome workaround. I knew it was the driver. I wound up selling mine and bought a new Mac mini.

Yeah, that was going to be my next move. But it would have been a pain to replace this specific use computer with a newer model. So I'm glad I found a solution (... for now!)
 
I did a clean install, and it was worse then what I had before. I called Apple and they told me their usual , turn off computer etc...I let her know about this forum and she said the only explanation she has is that after El Capitan Apple started using 64bit and the video cards probably weren’t handling well.

So I gave up , and installed Mojave . It’s a bit slow but useable. No pixel problem. I found a site where it tells you in detail how to install Mojave on older macs. For now no problems.
 
I did a clean install, and it was worse then what I had before. I called Apple and they told me their usual , turn off computer etc...I let her know about this forum and she said the only explanation she has is that after El Capitan Apple started using 64bit and the video cards probably weren’t handling well.

So I gave up , and installed Mojave . It’s a bit slow but useable. No pixel problem. I found a site where it tells you in detail how to install Mojave on older macs. For now no problems.

I assume you are referring to the dosdude site. I also assume that when you perform this patch it basically does the same thing: installs the OS without the specific drivers for the Radeon 6770. Without the drivers you would end up with a slow, but useable system. Dosdude DOES say that "Mojave will be almost UNUSABLE without graphics acceleration." He also says "You CANNOT disable the AMD GPU in an iMac." which seems to conflict with both my experience and yours.

Still seems like there COULD be a driver written for these machines that would work but I realize nobody will take the time to do so. Curious though if your experience with Mojave is any better/worse that what I am getting with Sierra right now. I did fix the screen corruption and crashing, but still get many display artifacts (minor) and issues with some programs like Firefox (which hangs after moderate use). Any major issues with your workaround?

Oh, and ONE MORE THING....
I just did the latest Security Update and guess what? After rebooting, the graphic corruption WAS BACK! Looks like the latest update saw the missing drivers and reinstalled them (including AMD6000Controller.kext with a build date of Feb 7, 2019.) So I guess this fix may have to be re-applied after some updates. I'd really be interested in why the AMD6000 kext was so recently updated; almost gave me hope that they might be trying to solve this issue...HA HA!
 
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I assume you are referring to the dosdude site. I also assume that when you perform this patch it basically does the same thing: installs the OS without the specific drivers for the Radeon 6770. Without the drivers you would end up with a slow, but useable system. Dosdude DOES say that "Mojave will be almost UNUSABLE without graphics acceleration." He also says "You CANNOT disable the AMD GPU in an iMac." which seems to conflict with both my experience and yours.

Still seems like there COULD be a driver written for these machines that would work but I realize nobody will take the time to do so. Curious though if your experience with Mojave is any better/worse that what I am getting with Sierra right now. I did fix the screen corruption and crashing, but still get many display artifacts (minor) and issues with some programs like Firefox (which hangs after moderate use). Any major issues with your workaround?

Oh, and ONE MORE THING....
I just did the latest Security Update and guess what? After rebooting, the graphic corruption WAS BACK! Looks like the latest update saw the missing drivers and reinstalled them (including AMD6000Controller.kext with a build date of Feb 7, 2019.) So I guess this fix may have to be re-applied after some updates. I'd really be interested in why the AMD6000 kext was so recently updated; almost gave me hope that they might be trying to solve this issue...HA HA!

Sorry for the late response. But it was to sluggish Mojave. I reinstalled leopard and had no issues at all but couldn’t use anything when it came related to cloud or some apps . I updated to the current OS X and the issue was worse. I have no clue why apple hasn’t been shamed for this .
 
Getting the same on a Mid 2011 21.5" iMac with AMD Radeon HD 6750M 512 MB graphics running macOS Sierra 10.12.6
[doublepost=1555183390][/doublepost]Ended up rolling back the OS. Living with the old software. It’s not graphics card it the OS updates. shame on apple...
 
[doublepost=1555183390][/doublepost]Ended up rolling back the OS. Living with the old software. It’s not graphics card it the OS updates. shame on apple...
I’ve (Johnny Ive) since updated this iMac to High Sierra 10.3.3 and still see graphics glitches.

Before I upgraded though I noticed that shaking the mouse pointer (to help locate the cursor) where it starts to show a large cursor allows me to “rub out” the graphics glitches as though you’re using an eraser tool in MS Paint! Very strange behaviour indeed and came across it by chance. I’ve now disabled the setting in SystemPreferences/Accessibility/Display to see if that may help alleviate the issue somehow? I’ve also noticed that the Mac freezes it’s screen (and therefore I have to reboot) often when I’m swiping between Spaces onscreen as it freezes during the transition between the Spaces.
 
[doublepost=1555183390][/doublepost]Ended up rolling back the OS. Living with the old software. It’s not graphics card it the OS updates. shame on apple...

What version did you rollback to?
[doublepost=1559173377][/doublepost]
I’ve (Johnny Ive) since updated this iMac to High Sierra 10.3.3 and still see graphics glitches.

Before I upgraded though I noticed that shaking the mouse pointer (to help locate the cursor) where it starts to show a large cursor allows me to “rub out” the graphics glitches as though you’re using an eraser tool in MS Paint! Very strange behaviour indeed and came across it by chance. I’ve now disabled the setting in SystemPreferences/Accessibility/Display to see if that may help alleviate the issue somehow? I’ve also noticed that the Mac freezes it’s screen (and therefore I have to reboot) often when I’m swiping between Spaces onscreen as it freezes during the transition between the Spaces.

Definitely the same behavior I experienced. My cursor would have large pixels around it as well. And although switching spaces wouldn't always reproduce the issue, it would after a few days.

I just ended up buying a new a 2015 iMac. Now I see the 2017 ones are on sale for a good discount too. I could really use those 2 Thunderbolt 3 ports right about now.
 
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Definitely the same behavior I experienced. My cursor would have large pixels around it as well. And although switching spaces wouldn't always reproduce the issue, it would after a few days.
AAAANNNDDD it's back! Dammit! Hasn't frozen as such yet, and not sure if this is related, but when trying to switch user, my external monitor went all red and iMac screen looked like it was somehow set to the secondary monitor because it didn't show the login/switch user prompt but everything was blurred over like the secondary screen normally is. Unplugged monitor, iMac showed login prompt and then plugged external monitor back in and now all good. Definitely worrying me at this point how much longer she'll go on for!
 
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