No You can only use a GPU that was used by Apple As OEM so if you had an AMD Radeon R9 M290X graphics processor with 2 GB of dedicated GDDR5 memory you could put in an AMD Radeon R9 M295X with 4 GB of dedicated GDDR5 memory if you could find one at a reasonable price. Also selling your old card wouldn't be too profitable as only someone with a damaged card would be a potential buyer. The machines are so new a damaged GPU should be a warranty repair .
You'll have EFI (aka bios) and extension (aka driver) if you attempt to put just any old GPU in any Apple computer.
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