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iMac 2009 shows terrible graphic glitches!

garirry

garirry

macrumors 68000
Original poster
Apr 27, 2013
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Canada is my city
I was editing my video in Final Cut Pro X, then suddenly, a bunch of lines and blocks and shapes appeared on my screen (graphical glitches). This happened to me back in April this year, I turned the LCD smoothing off, and never had this problem again, until today. I first tried to just restart the computer and ignore the problem, but it came back. I highly suspect that this is still a problem in OS X Mavericks. Can anyone confirm this or tell me what is the problem? If it's a software issue, I will downgrade to Snow Leopard.
 
You could post a picture or a link to some video of it, but I'd much sooner suspect a failing GPU rather than software with graphical glitches like random lines, blocks and/or freezing.
 
Well, here is a picture of how it looked like when I had the issue in April, currently, it's still similar. Let's suppose that the issue is the graphic card. What can I do in this case? Can I replace the graphic card or is it soldered/fused to the logic board? I mean, I don't have much money to spend on repairing the computer.
 

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That does look a lot like a failing GPU. They can be replaced without replacing the whole logicboard in that model iMac. But they can be costly to replace.
 
Intell said:
That does look a lot like a failing GPU. They can be replaced without replacing the whole logicboard in that model iMac. But they can be costly to replace.
Click to expand...

Does it just require soldering or does it need more complicated processes? Also, where can I buy that graphic chip, and which ones work with my iMac model?
 
The hardest part is opening and removing the logicboard. The GPU is on a video card and the whole card is replaced. You must use one from another iMac of the same or very similar model.
 
Yeah, that most definitely looks like a GPU on its death bed.

As Intell mentioned, replacement of the GPU itself is possible if you can find the part. Here is a guide from iFixit.

Some have also reported success by doing a reflow, basically putting the GPU in an oven at 200° for about 8 minutes to re-solder all the points on the board.

It's certainly worth a try before investing in a replacement part.
 
Just a quick note, I have a 21.5" model, I'm not sure if the graphic card replacement is only for the 27" model. And it's expensive. I'm gonna try to cook the graphic card, see if it works.
 
So, quick update everyone.

I have used that computer for two days straight, however without using Final Cut Pro. I suppose that the graphic card isn't fully destroyed, it's just that it's incapable to use its maximum power. When you overclock a graphic card, you may see certain graphical glitches, which mean that the graphic card isn't capable of handling the power you're asking for.

Just wondering: Will underclocking my graphic card help reduce the amount of graphical corruption?

Also, what exactly causes graphic card death? Is it just depending on the model, how I use it, how often, how much?
 
I get it, but is it possible to prevent the graphic card from experiencing the issues by underclocking?

And a repeat of my other question: What usually causes the graphic cards to become corrupted?
 
garirry said:
I get it, but is it possible to prevent the graphic card from experiencing the issues by underclocking?

And a repeat of my other question: What usually causes the graphic cards to become corrupted?
Click to expand...

Sure it might, but afaik there is no way to underclock the GPU on the OSX side.
 
garirry said:
I get it, but is it possible to prevent the graphic card from experiencing the issues by underclocking?

And a repeat of my other question: What usually causes the graphic cards to become corrupted?
Click to expand...

In theory it sounds like a good idea.

Don't stress the GPU and it won't show sighs like that.

There is no way to underclock the GPU in OS X. However you can take some load off your graphic card by not doing anything graphic intense. (No Games, No Video editing, light flash work). It will die completely eventually.
 
The graphic card can't be under/overclocked because it's on OS X or is it because the graphic card itself is made to be incompatible? Can I just install Windows on Boot Camp and underclock the card?
 
garirry said:
The graphic card can't be under/overclocked because it's on OS X or is it because the graphic card itself is made to be incompatible? Can I just install Windows on Boot Camp and underclock the card?
Click to expand...

You can usually change the video card clocks on a Windows Bootcamp (I've overclocked my card that way). A utility like Sapphire Trixx or MSI Overdrive will do it.
 
To underclock the graphic card in OSX is much more complicated than under Windows.

1st of all, the card's ROM must be unlocked. Otherwise, it's impossible to underclock that card in OSX.

Then, you have to find out all the underclock setting (voltage, clock speed, etc) in Windows.

Dump the ROM image, edit it, and then flash the new ROM image back to your card.

This is not an easy task. It may brick your card. You may lost the EFI part (no boot screen until OSX loaded). It may even damage your motherboard (e.g. A wrong power setting cause it to draw too much power and burn the motherboard).

Therefore, it's not recommended unless you really know what you are doing and fully prepared for it.

Even though it can increase the stability. That problem may come back in few months and you have to further lower the clock speed or increase the voltage.

Anyway, your screen captures make me suggest that both the GPU and the VRAM has protential problem. Replace the whole graphic card may be the only solution.
 
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