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haravikk

macrumors 65816
Original poster
May 1, 2005
1,499
21
So a friend of mine has an old iMac6,1, the old white Intel Core Duo 2 machine with a 24" screen, always was a sweet machine.

Now I was supposed to just be helping to install some software but I'm encountering an issue that I'm having a ton of trouble diagnosing; it's a series of graphical glitches. Now, sometimes the machine runs fine for hours without a hitch, other times it starts getting lines of corrupt pixels, or even goes all out with corrupted icons, pieces of windows being left behind, window borders not appearing and so-on, leading to a badly corrupted mess.

I've already done a clean install of Lion (was going to do it anyway), and I've tried the usual suspects. I got the correct copy of the Apple Hardware Test but it turned up nothing, likewise TechTool Pro 6 couldn't find anything wrong.

Despite no errors for RAM I decided to try swapping the sticks out anyway (one hynix 1gb, one Crucial 2gb) but both exhibited the issue (in either slot). Most annoying is that the issue seemed to occur less quickly in some configurations, but I think it's just part of its nature as the issue is very random; sometimes the system will run for a while without issue, other times moving a window as soon as it starts up will cause the problem, making it very frustrating (no clear pattern or trigger).

I managed to get the bezel off to take a quick peak under the hood and the machine looks clean; i.e- no obvious signs of dust build up to cause overheating, and with smcFanControl I can spin up all the fans without issues. I didn't disassemble the machine any further as I'm not completely sure what more I could do, is it likely that the machine is dusty if there's no visible signs beneath the screen (i.e- with only the bezel removed)?

So, are there any other obvious culprits? My first, and continuing thought, is that it's an issue with the graphics card, but I don't expect there's much hope of replacing that cheaply these days, and I'm not sure I'd want to risk it unless I can confirm without a doubt that it's the cause of the problem (as it'd be £100 wasted if I can't resell it). Are there any tests I can run to confirm for certain whether the issue is GPU related?

And here I was just supposed to be installing Photoshop, but I don't know if it's a good idea to risk it on a machine with a possibly faulty GPU!
 
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