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

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iMac HD6970m GPU Upgrade Failed

Hi

I purchased a second hand "working" HD6970m off eBay and installed it in my iMac. What does work is the boot screen (initial booting as well as the boot disk select option).

Problem is when I go passed this point the boot freezes giving the warning "waiting for boot device" on a white screen. I get the same result whether I select the boot drive or USB Yosemite installer or recovery partition.

I've tried the usual SMC and PRAM resets.

I manage to boot into bootcamp (I can hear the into boot chime and the shutdown chime) but the screen stays black. I tried F8 to boot into safe mode but also no luck.

Is it possible the card is faulty? What could cause the boot error?

Any help will be greatly appreciated.

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You appear to be dancing around two different issues here: Graphics bd swap out & HD issues.

Can you fill us in on why you are exchanging the graphics board. Was the original one working and if so what the system working.

Your issue with the HD implies the boot drive has problems. Do you have a bootable external drive? I would try booting up with it to see if that works.

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What initially happened was the GPU upgrade seems to have "bricked" the mother board for lack of a better term. To "unbrick" the board I simply followed a recommendation (found it somewhere not the net) and, after replacing the original GPU, I attached a normal spinning HDD to the board as apposed to the SSD, and everything booted back up no problems.

I then tried again with HD6970 and got the same result - "waiting for boot device". This time however when I swapped back to my original GPU everything booted fine.

So currently i'm only stuck with the non-co-operative HD6970.

Could it be a static issue? Could it be a hardware conflict causing the boot error? Could the card be a dud?

If the GPU is faulty why do I get an initial boot screen?

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Altering graphic cards can be iffy. It sounds like your replacement board is not compatible with this system. Apple has different EFI firmware levels for different series of systems which interfaces with the graphics card. You could try checking the firmware to make sure its up to date otherwise I don't see any options here. Here's the Apple TN to guide you on checking and upgrading: EFI and SMC firmware updates for Intel-based Macs

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