iMac Intel 27" EMC 2309 (Late 2009, Core 2 Duo 3.06 or 3.33 GHz) ID iMac10,1, EMC 2374 (Late 2009, Core i5 2.66 GHz or Core i7 2.8 GHz) ID iMac11,1

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Graphical errors and system stalling at boot up

Hi everyone. I hope someone here can help me nail the issue here with my iMac. I have a range of symptoms, that doesn't really pinpoint to anything specific I think, besides perhaps some global components like the motherboard.


How it started:

Found my computer today completely black. It was on earlier, and it looked like it had done a serious crash. I shut it down by holding in the power button for a while and then I it started again.



It starts with a chime, meaning (POST) internal tests came through right?

Now it started off with bars or thin green lines repeated regulary vertically.


(image shows verbose startup)

Block Image

When the apple shows up, the distortion changed into small squares that covered the screen in a repetitive pattern.


Block Image

That is usually as far as it will boot. Although once it got to the user login screen, but froze there.

Throughout the issues, I am able to move the mouse on the screen. Even if everything freezes. The energy saver dimming of the screen works.

Second screen connected will flicker yellow and white.

I was not able to boot up emergency disk partition.

But was able to boot up the install CD once. The graphical issues went away then, and I ran repair disk/repair perms with out any help. Later attempts to do this have failed.

I was not able to boot up a separate system on a usb disk. It freezes into the apple part of the process.

Was not able to access ATH. It froze later in before anything showed up.

I've reset the SMC and PRAM.

I've disconnected everything except ethernet, mouse, keyboard.

The mouse cursor hovers above the graphical artifacts. So its not the screen hardware.


Conclusions so far:

- If it was a hard disk issue, I shouldn't have any problems booting from a CD right?

- If its a graphics card issue, It shouldn't freeze at the apple logo? Can graphics card issues cause system freezes? Since I was able to move my mouse, that means its not a full system kernel panic right?

- Motherboard?

- power supply?

- faulty ram?

- It kind of feels like there is some corruption in a hardware component firmware or something.

- Don't think its heat related as I had it off for an hour to see if that help, and it didnt.

Would really appreciate any help on diagnosing this, as I will have to cash out for repairs, or hopefully do it myself.

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I have a 2010 27" machine in for repair with the red spots like your #2 photo. I'm replacing the the video card and will let you know if that fixes the problem.


1. I managed to install the new graphics card

2. while with the beast open, I also successfully installed an SSD

3 BUT, when closing it up, I manage to rip the display connection socket of the motherboard. I sent it to get repaired to a company south of England, who sat on it for a few weeks and gave up on getting the fiddly socket on. And thats where it's at at the moment.

I'm currently looking at more specialised resources closer to home who can help me replace the socket, but I am currently out of funds to cover it, so at the moment I am using the iMac with only a secondary monitor attached.

So a big warning to you if your are opening/closing your iMac, take very much care on handling the 4 cables attached to the main screen. Especially the flat cabled display cable. I've found other posts here in ifixit complaining about this socket, and how it seems to be a sort of a booby trap for the unaware. Not great build quality on it, and easily damaged. Otherwise, the ifixit guides were excellent!


I'm having somewhat similar issues, although not as severe. The system boots and runs fine, but sometimes the shadows from windows become glitchy. See here for an example. The cursor and other windows layer properly, so I know it's a graphics issue, although I'm not sure where it originates. I find that sometimes quitting everything (including things such as the Dock) and relaunching Finder fixes the problem, but not always – sometimes I have to restart the entire computer.


This only begin after I upgraded to OS X 10.9. I'm on a MBP 15" mid-2010, nothing special installed.

Any ideas?



Could be the graphics card. Or overheating. Is it like this after being off for a while? Or does it come on after being in use for a bit? If so, it could be some heating issue. Try connecting a second monitor, and see if the other screen has it too. If so, it could be the graphics card.


Could be. I really don't know why it's doing this. Sometimes as soon as I start it up, sometimes only after I've been using it for a while. Sometimes on the integrated graphics, sometimes on the dedicated graphics card. It seems that it happens more often after I have to force quit something, but this isn't always the case.


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Because you're also seeing video problems on the external monitor it points to Video Card/Logic board problems.

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Thanks for the response. I wonder if there is a way to figure out wether its the motherboard or graphics card.


Boy - thats a good question - I wish I had a good answer to give you. How much time and money you're willing to throw at this is something only you can determine. Some of these you can swap Video Cards on (I don't know if this is one of those models)... to do that is a lot of work and you'd have to use OEM or OEM Upgrade video cards... you cant just go find one that fits the socket you'll have EFI and upgrade/driver problems. The shade tree mechanics method would be to try the least expensive part first - I don't know which that would be either.


I hope its not the mother board or any other component than the graphics card, as I have ordered a used one from the 2010 imac that should fit in. With i the ifixit guide i will replace the card and hope that fixes it. :O


Be sure to come back and report good news, or bad.


How'd it go? I have the same issue, and was considering the same fix.


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Man. So sorry I didn't reply on this thread. It went well to a certain point. While I was at it I installed a SSD as well.

The only issue is that I damaged the connection point to the main display on the motherboard. Later research showed me that this is not unusual, and that this part of the deconstruct of the computer is considered a bit of a booby-trap, so be careful when you disconnect the screen. It's the big flat lead that the screen connects too.

I bought the replacement socket that got damaged on the motherboard, but no luck in finding anyone who has enough expertise or equipment to replace the socket. If there is anyone in the Bristol area (UK) who think they can help, give me a shout.

Since then, I still used the iMac fully, only though with a secondary screen. The SSD was a great upgrade, and speeded up the computer massively.

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H Landsem will be eternally grateful.
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