Model A1200 with 2.16 or 2.33 GHz Core 2 Duo processor

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weird screen glitches and freezes, can't be force-quit.

Hi, is it OK to follow up or should I open a new thread?

My parents have an 2006 iMac (model name: iMac4,1) Intel Core Duo, 2 Ghz. that suffers from weird screen glitches and freezes, that can't be force-quit.

Accoording to the system profile (sorry, it's in Dutch):

Modelnaam: iMac

Modelaanduiding: iMac4,1

Processornaam: Intel Core Duo

Processorsnelheid: 2 GHz

Aantal processors: 1

Totaal aantal cores: 2

L2-cache: 2 MB

Geheugen: 2 GB

Bussnelheid: 667 MHz

Opstart-ROM-versie: IM41.0055.B08


ATI Radeon X1600:

Chipsetmodel: ATY,RadeonX1600

Type: GPU

Bus: PCIe

Breedte PCIe-baan: x16

VRAM (totaal): 256 MB

Fabrikant: ATI (0x1002)

Apparaatcode: 0x71c5

Revisiecode: 0x0000

Versie EFI-besturingsbestand: 01.00.068



Resolutie: 1680 x 1050

Pixeldiepte: 32-bits kleur (ARGB8888)

Hoofdbeeldscherm: Ja

Synchrone weergave: Uit

Online: Ja

Ingebouwd: Ja


Status: Geen beeldscherm aangesloten

For now, it seems to happen only when it gets warmer, after a while. Is there something I can repair myself on this?

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1 Answer

Chosen Solution

Typically video abnormalities (lines, stuck pixels, jagged lines, etc) and freezing seen together are a result of a failed/failing video card. You might boot the Mac in Safe mode (hold Shift while booting, you can let go once you reach the Apple w/ spinning gear) to see if the problem persists, if it does then you can likely rule out a software issue.

The ATI Radeon X1600 cards in these did seem to fail somewhat more frequently than other models but not quite widespread enough for Apple or ATI to initiate a repair extension program. A quick search though shows a video of someone with what sounds like similar symptoms on a similar iMac. video of distorted video on iMac

It's likely a safe bet that the video card is the culprit here. If you can source a replacement (ebay,, etc) then you can use the guide below to replace it.

Video card replacement in iMac

Good luck!

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