I replaced the NVIDIA 130GT w/ a 4850 AMD Radeon card from a 27" imac, same year (late 2009). Computer boots, all 4 LEDs go on, computer accessible from remote screensharing on the LAN so is obviously up and running. No picture on the screen (backlighting working).

I think it's an EFI/firmware problem w/ the new card. Any ideas as to a work-around? Edit the BIOS in the GPU to match the 24 inch screen or the Logic board ID? Thoughts? Thanks!

  • 2
    does it start up in Safe mode or Single user mode?
    – Ruskes
    Jun 4, 2014 at 6:59

1 Answer 1


It starts fine, but no image on the screen. Clearly think it's a GPU-CPU issue, but obviously they are talking or all 4 LED's wouldn't light up....so it must be something written into the EFI that's preventing screen imaging, I'm thinking.

  • You should comment instead of post an answer Jun 11, 2014 at 12:04

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