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Crusoe · Jun 21, 2008, 09:58 PM

Hi all,
My 24" with the 7600GT is starting to have serious texture tearing in all games and lines across the screen when not gaming.
Since the 7600GT is a card would replacing it fix the issue? Out of warranty of course.

I ran the exhaustive diagnostic and it found no issues. Also put a temp and fan monitor widget in. The GPU doesn't show or have a fan which I find odd. Should iStat Pro show a fan or maybe fan was broke?

Temps after gaming for 3+ hours
51C GPU
57 GPU Diode
51 Heatsink
Doesn't seem too hot.

Any advice on fixing issue would be great.

Simon · Jun 22, 2008, 01:17 AM

Those temperature are absolutely normal. Have you run Apple Hardware Test (on your intsall DVD) to get actual error descriptions?

Your GPU is on a daughter card which can in principle be replaced. The problem is getting that card. An AASP can get it from Apple and swap it in, but you will not be able to buy the card at any store and put it in there yourself. I would get the AHT error codes and check an AASP to see what they would charge should a replacement be necessary.

Crusoe · Jun 22, 2008, 01:25 PM

I ran the AHT, no errors. I had a g4 powerbook that the gpu was failing on and AHT showed no errors.

If the labor is too much I hope the AASP will order the part so I can DIY. I've opened every Mac I've ever owned (6100, 4400, Cube, TiBook, 17" PB, 12" PB) except this iMac and don't have any apprehensions about working on it myself.

So the 24" doesn't have a GPU fan?

Simon · Jun 22, 2008, 05:22 PM

It doesn't have a fan just for the GPU. It does have a fan that cools the heat sink connected to the CPU and GPU through heat pipes though.

P · Jun 23, 2008, 07:06 AM

I suggest reinstalling the latest combo update, as well as any graphics updates that might available (you don't mention which OS you're running). That could easily be a driver issue.

Crusoe · Jun 24, 2008, 04:02 PM

I considered drivers but it slowly gets worse the longer I play which had me worried about heat. I will try to download and rerun combo install before talking to an AASP. I'm running latest of leopard.

joe · Jun 28, 2008, 11:05 AM

Here's one source for the NVidia 7600GT used in the 24" CTO iMacs:

661-4180 24" iMac NVIDIA GeForce 7600 GT VRAM 256MB Video Card, Apple Mac and iPod Accessories

From the photo, it looks as if the price includes the heat sinks and heat pipe.

PLin · Jul 4, 2008, 12:39 PM

I have the same iMac, and I started noticing similar problems a few weeks ago while we were having a heat wave. Now that the weather has cooled down, the problems haven't gone away, so I just dropped it off at the Apple Store for repair, since I have AppleCare. They ordered the part number mentioned in the previous post, so that will probably fix your problem too.

In the Apple Discussion Forums, it seems that others are experiencing the same issues. Many people are past their 1 year warranty but have successfully fixed the problem by using smcFanControl:

smcFanControl2

It's obviously not a permanent fix, since it's software, but if it works, then why not use it.

Crusoe · Jul 23, 2008, 03:56 PM

Update: I had the card replaced and the problem is gone and so is ~$350 (not too bad, but not good either). Played for some extensive session without issue on pretty warm days.
It appears Apple didn't take into account keeping this GPU cool enough so I'm gonna us the fan tool as well.

REVBCO · Jul 23, 2008, 05:01 PM

I was having the same problem with my imac. Lines and all, especially when it got hot.
Its a CTO with the NVIDIA 7600GT. I took it in last night and Apple said that it must be the hard drive. We will see when I get it back.

I will post an update then.

kmkkid · Jul 23, 2008, 06:34 PM

It's not the Harddrive. It's a failing GPU.

Same symptoms happened with my CD iMac with x1600 about 2 months after the first year warranty was up. After calling apple about another computer I mentioned that this had happened to my older iMac and they actually gave me a free service call and the technician was nice enough to have my Logic Board replaced - even though it was almost a year out of warranty.

Now my computer doesn't have any of these issues.

I suggest calling Apple and telling them that this is a common problem and see if they'll fix it out of warranty.

Crusoe · Jul 23, 2008, 08:07 PM

Let us know. It took a while before I found some others that had the same card that had this issue.

kmkkid · Jul 24, 2008, 12:02 PM

Originally Posted by Crusoe

Let us know. It took a while before I found some others that had the same card that had this issue.

http://discussions.apple.com/search....5&rankBy=10001

The make of the card doesn't matter. The iMacs are too hot and cause overheating of the GPU in many units.

It's a very common problem, and not related to the hard drive at all.

In fact I don't even know why Apple would suggest the hard drive after knowing about these issues. And usually graphical distortions are caused by a bad GPU or RAM, never seen a hard drive ever cause these anomalies.

REVBCO · Jul 28, 2008, 11:33 AM

Going to pickup my imac today. We will see if the problem is fixed.

B

REVBCO · Aug 1, 2008, 12:55 PM

Update...

Got the iMac back and started to install my software and the lines started to show up again. So I took in back and they are going to put a new graphics card in. Hopefully that should solve the problems.
On the bright side I got a fresh 500GB hard drive out of all this.

B