Practically all of the differences between AGP cards of the same class (Mach 64, Rage 128, Radeon) are in their initialisation. This is probably still done by the ViewFinder firmware before RISC OS 6 silences it. The RISC OS 6 driver for ViewFinder, therefore, hardly needs to deal with differences between AGP cards of the same class. Mostly only with acceleration. And even between classes, there are very few differences in implementing acceleration.