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macrumors newbie
Original poster
Feb 12, 2012
Hi Guys
Ive just managed to get a PC ATI 4870 working my Mac pro 1.1 and with the Apple bootscreen but something strange is happening. I found some instructions on on how to create a mac rom from the pc rom by adding the efi part to it.

Now heres the odd bit.

It will only boot in slot 2 with with the pcie system config set at x1 if you change it to x8 it refuses to be seen. If you stick it in slot 1 as it runs at x16 it cant be seen.

I know slots 1 and 2 work as i still have the old nv7300 and been testing.

Ive also tested other 4870 roms, again it wont work in slot 1 at all and x1 in slot 2

Any thoughts?
Last edited:


macrumors 6502a
Jul 17, 2012
PowerPC land
Possible solution


It sounds like the slots are mixed up. Go to your system folder on the root of your drive. Look for "CoreServices(folder with an X). Find Expansion Slot Utility and run it.

Its possible the slot configuration might be off. This utility(only works on 1,1 Mac Pro) might resolve the problem.


macrumors 68040
Dec 7, 2009
Try to reset PRAM. I've had similar issue: my card was able to run only x8 and Slot Utility was saying that's maximum speed. PRAM reset fixed this.
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