MP 1,1-5,1 Mac Pro 1.1 / El capitan Black Screen with Apple ATI Radeon 4870

[explit]

Hello guys!

I have an Mac Pro 1.1 (Upgraded to 2.1) and installed an modified Version of MacOS 10.11.6 El Capitan
The original Video Card Nvidia GeForce 7300 GT 256Mb have issues with El capitan (It recognise only 9MB of VRAM and have glitches)

I want to install an original ATI Radeon HD 4870 512MB, which was originally shipped with Mac Pro 4.1.
I connected the both Power cables from the Mainboard, but i get an black screen on Mac Pro 1.1

On Mac Pro 4.1 the card work just fine.

As i already said, its an original Mac Pro 4.1 Graphic Card, with original Mac ROM, but maybe it has some problems with 32bit EFI of Mac Pro 1.1

Can somebody tell me, which ROM i need to flash, to get this card working under Mac Pro 1.1 ?

Thanks !

 

[Macschrauber]

4870 have dual efi, they have bootscreens with 1.1 to 5.1

do a complete nvram reset, 3 times in a row

 

[explit]

OK, thank you very much!

 

[explit]

Thanks to @Macschrauber - after PRAM-Reset 4870 works like a charm!