@Andreas_Wolf
Thanks for detailed explanation. I have to read this three times
So if I summarize it ( with help of www.techpowerup.com ), the fastest powerpc big-endian linux 3D capable cards should be TeraScale 3 with Cayman chip:
dual-slot: HD 6970 - 250W
single-slot: AMD FirePro V7900 with external power connector 150W or
AMD FirePro V5900 without external power 75 W.
Maybe also with Antilles chip HD 6990, but it has two graphics chips on one card and 375 W, a little bit overkilll.
AmigaOS3: Amiga 1200
AmigaOS4: Micro A1-C, AmigaOne XE, Pegasos II, Sam440ep, Sam440ep-flex, AmigaOneX1000
MorphOS: Efika 5200b, Pegasos I, Pegasos II, Powerbook G4, Mac Mini, iMac G5, Powermac G5 Quad