Small update: Looking for the device ID I've found an AGP-equipped PC and installed my X1950 Pro, but with no luck - the screen stays black. Maybe it's not MorphOS fault but just another bricked gfx card. I'll investigate some more.
what machine are you trying to put this card in?
It's been over a decade, but from my adventures flashing a radeon 9600 for my powermac3,3 I remember some electrical incompatibility in addition to needing a new ROM. Two pins on the card needed to be either scratched off, or in my case I covered them with electrical tape so that the mod was reversible.
I found some more recent source