Can someone tell me what is wrong with my 3 year old iMac?

Welcome to Mac-Forums..

Graphic tearing issues like the one in your picture is usually indicative of a failure of the GPU. But before we assume hardware failure, let's see if it could be something else..

Does it happen immediately after power-up? Does it happen after a certain duration of operation? Does it happen in Safe Mode? Was anything recently installed that made it happen more often? How long has it been happening?

Raz0rEdge said:

Welcome to Mac-Forums..

Graphic tearing issues like the one in your picture is usually indicative of a failure of the GPU. But before we assume hardware failure, let's see if it could be something else..

Does it happen immediately after power-up? Does it happen after a certain duration of operation? Does it happen in Safe Mode? Was anything recently installed that made it happen more often? How long has it been happening?

Click to expand...

Thanks for the reply! The first time it happened was the night before last night- I was scrolling pretty fast through fonts on Photoshop. I rebooted a few times and it would just sit there for a long time on the grey screen with the white apple. I then shut it down and unplugged/ plugged it back in and it came up just fine. The pixelating happened again this morning, we restarted the computer and it happened again- 3 hours later. This time I just waited it out and didn't shut down. Back to normal after about 5 minutes. Nothing new installed. Not sure about safe mode.

bblaine29 said:

Thanks for the reply! The first time it happened was the night before last night- I was scrolling pretty fast through fonts on Photoshop. I rebooted a few times and it would just sit there for a long time on the grey screen with the white apple. I then shut it down and unplugged/ plugged it back in and it came up just fine. The pixelating happened again this morning, we restarted the computer and it happened again- 3 hours later. This time I just waited it out and didn't shut down. Back to normal after about 5 minutes. Nothing new installed. Not sure about safe mode.

Click to expand...

This problem sounds intermittent...is this true? If so...two questions:

1. What percent of the time (approx.) do you have to deal with this issue? Such as how much time can you on average use the computer before this happens. And then if you restart the computer...does it go away immediately...or do you have to wait a while before the computer will work ok again?

2. Does the problem seem to only happen when you are doing certain computing tasks...or running certain applications?

- Nick

Also..... I would download the free iStats Pro widget and use it to monitor the three fans and various temperatures in your iMac. That might tell you something when the graphics goes south again.

chscag said:

Also..... I would download the free iStats Pro widget and use it to monitor the three fans and various temperatures in your iMac. That might tell you something when the graphics goes south again.

Click to expand...

We're thinking the same thing. Investigate possible heat/temp issues before declaring a possible gpu/logic board problem.

- Nick

pigoo3 said:

This problem sounds intermittent...is this true? If so...two questions:

1. What percent of the time (approx.) do you have to deal with this issue? Such as how much time can you on average use the computer before this happens. And then if you restart the computer...does it go away immediately...or do you have to wait a while before the computer will work ok again?

2. Does the problem seem to only happen when you are doing certain computing tasks...or running certain applications?

- Nick

Click to expand...

Hi, the only times it has happened is what I described in my last post-

"The first time it happened was the night before last night- I was scrolling pretty fast through fonts on Photoshop. I rebooted a few times and it would just sit there for a long time on the grey screen with the white apple. I then shut it down and unplugged/ plugged it back in and it came up just fine. The pixelating happened again this morning, we restarted the computer and it happened again- 3 hours later. This time I just waited it out and didn't shut down. Back to normal after about 5 minutes."

One time I was scrolling through fonts in photoshop (drop down menu), not sure what my husband was doing when it happened to him, and the last time was also drop down menu triggered.

chscag said:

Also..... I would download the free iStats Pro widget and use it to monitor the three fans and various temperatures in your iMac. That might tell you something when the graphics goes south again.

Click to expand...

I have that. This is what it is now.



The fans are fluctuating at about 1000, 1100 and 940 respectively. This is without pixelating issues though. I am afraid I won't be able to see iStat during an episode.

I should mention that I am uploading photos onto the internet.

Given that the problem hasn't been too frequent as of yet...and that the computers temps look fine...here's where things can get a bit more involved.

Here are three things to try:

- Do an SMC reset:
Intel-based Macs: Resetting the System Management Controller (SMC)

- Do a PRAM/NVRAM reset:
About NVRAM and PRAM

- Download, install, and run the free program called "Onyx":
Titanium's Software • Index page

For Onyx...just run the automated tasks (there's a button for it).

- Nick

pigoo3 said:

Given that the problem hasn't been too frequent as of yet...and that the computers temps look fine...here's where things can get a bit more involved.

Here are three things to try:

- Do an SMC reset:
Intel-based Macs: Resetting the System Management Controller (SMC)

- Do a PRAM/NVRAM reset:
About NVRAM and PRAM

- Download, install, and run the free program called "Onyx":
Titanium's Software • Index page

For Onyx...just run the automated tasks (there's a button for it).

- Nick

Click to expand...

Thanks Nick! I will try that.

We should mention that it still could be (and in fact most probably is) a graphics subsystem issue. What video card do you have in it (should be available under "about this mac"'s advanced function if you're not sure).