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Problem with nvidia geforce 8800 GS in early 2008 iMac

OK, so about a week ago I bought a second hand early 2008 24'' iMac off of someone. He had told me that it had a problem before I bought it (but even if he didn't, I wouldn't be terribly upset. He practically gave it to me). He showed it to me through skype and everything and it appeared to be completely usable, as it would only show screen artifacts after a little while. WELL, the computer is now mine, and I can confirm that it indeed has a problem, but one that is a wee bit more serious.


Basically, if I boot it with a "cold start", or start it when the aluminum is literally cold to the touch, it will boot perfectly fine, and it is a completely usable machine. But, if I try to do something that requires a bit of graphical power, like loading the "effects" pane in Photobooth, the screen flashes once and the whole computer, sometimes with the exception of the mouse, locks up and is completely unusable. Sometimes it will recover itself and can be used a little more, but it just ends up locking up and freezing again and generally cannot recover after that. If I hard reset it and then boot it again after that (within I'd say one to two hours of turning it off), the computer will do one of these:


  1. it will boot with a bong, then it will show Apple logo, the little wheel will start to spin, but once it's time to load OS 10, the Apple logo will start going all fuzzy and screen artifacts will appear to the left and right of it, or sometimes it will flash orange. Basically when it's time to load the OS, it will just so something really unusual.
  2. It will boot with a bong, and then the apple logo will appear, but be fuzzy initially. Or it will show a solid logo, but it will gradually deteriorate overtime.
  3. The computer will bong, then either the bottom half, or the whole screen will strobe. This is my least favorite as it is quite painful to my eyes
  4. The computer will bong, show a black screen, then it will bong over and over again until a hard reset is performed.
  5. The computer will bong, then show a sort of interlaced screen with the left half being white, and the other being black.
  6. (usually happens when booting to the SuperDrive), computer will boot with a fuzzy Apple logo, then it will show a fuzzy screen saying that the computer needs to be restarted.


I think you get the idea. Also sometimes the computer will actually boot into OS X behind the fuzzy Apple logo (meaning I can actually do stuff in OS X, but my screen is obscured by a fuzzy Apple logo). So yeah, my question is, is it the graphics card, bad RAM, both, or could it be software related? I HAVE managed to slowly erase the formally known as "Chococat" drive (which is now the appropriate Macintosh HD), and install OS 10.6 on it. However it still does this. I also have removed the MASSIVE boot camp partition on it, which gave me back around 258 gb for use with OS X (yeah, the original owner actually partitioned the disk so that 258 gb of the disk was for either vista or 7, and the remaining 20 was for OS X).


I can use the computer just fine in Safe mode, but it is too restricted in that mode and it's not a fun experience in safe mode. SO, yeah sorry about the massive post but if you could help that would be AWESOME! I can also maybe if the forum will let me, post some videos of the iMac doing what was listed above. OK that is all for real 😀

iMac, Mac OS X (10.6), early 2008 model 24 inch

Posted on Jun 21, 2011 6:13 PM

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Posted on Jun 21, 2011 6:19 PM

It sounds like a failing HD or graphics card. Run Apple Hardware Test, if you don't have the original Install Discs that shipped with the computer ask the seller if he has them. If not you will need to call Apple and purchase a replacement set (they're specific to your serial number), the cost should be nominal. If it comes up with errors Google them, otherwise you will need to take it into an Apple Store or AASP to be professionally diagnosed.

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Question marked as Best reply

Jun 21, 2011 6:19 PM in response to Pizzscn

It sounds like a failing HD or graphics card. Run Apple Hardware Test, if you don't have the original Install Discs that shipped with the computer ask the seller if he has them. If not you will need to call Apple and purchase a replacement set (they're specific to your serial number), the cost should be nominal. If it comes up with errors Google them, otherwise you will need to take it into an Apple Store or AASP to be professionally diagnosed.

Problem with nvidia geforce 8800 GS in early 2008 iMac

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