iMac mid-2011 GPU is Pants

Lately I’ve found myself playing around with a bunch of iMac’s to fix or upgrade them. The 2011 edition’s particularly seem to be more readily available at reasonable prices now and with an SSD still perform very well. I was particularly interested in the 2011 edition as it comes with dual Thunderbolt/DisplayPort ports and I will really hoping to use this for a 3x 1440p setup at home.

The Problem

My experience with 2009 and 2010 iMacs had been that display issues with them are often backlight related and therefore when I saw a second hand mid-2011 27” A1312 iMac 12,2 pop up for sale I foolishly assumed that all I would need to do is a swap out of another backlight or LCD that I have spare and all would be well. Oh no! In fact about 30 seconds on Google would have showed me that infact this model is notorious (like the MacBook Pro 2011) for having quite flakey GPU’s. So much so that there was a replacement program lauched in 2013 for the affected models. The program has since expired and TBH honest, its probably unfair to expect after sales service on a 6yr old machine (I tried it on with Apple but no joy there).

The issue with the GPU apparently is that after years of heating up and then cooling constantly, the the chipset and the board start to seperate meaning in some cases that the display has lines running through it, strange colouring or just turns off after a peiod of use. Mine had purple lines running vertically through it and then wouldn’t complete booting up. It was possibly to get it to boot if you removed all of the AMD* kexts from /System/Library/Extensions but the machine is not really useable in this configuration.

Some users have had temporary success taking their broken GPU and putting it into the oven at 200c for 10-12 minutes. Apparently this is able to re-melt the solder such that the connections between the chipset and the board are re-established. Not a very exact science and according to some, just plain silly.

Maybe Solution

One spare part I did have lying around is a 2009 iMac GPU, the Radeon HD 5760m with a whopping 256MB RAM. Low and behold it fit (being standard MXM) along with its cooler and the system booted correctly into MacOS. Great result! However; the Thunderbolt \ DisplayPort ports are not lightly up my external displays. Damn! I’m guessing there is a firmware limitation or something at play here.

Options

eBay has yielded some hits for new / reconditioned GPU’s for this iMac but unfortunately they are priced at more than the iMac itself. And my slight fear is how well recondition they actually are.

Another eBay seller “Brickfence” will take your broken GPU and recondition it for you with a new chipset. This is slighly cheaper than the above but still a bit of a stretch. And I can understand why - having watched a few YouTube videos of the removal and re-installtion of the chipset, this is not childsplay by any means.

Now my plan is to keep my eye out for another broken 2011 iMac (21.5” or 27”) that has an intact GPU.

To be continued..

@cd