> 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.

Yes, performance ranking of cards with RV970 "Cayman" GPU would be:

1. Radeon HD 6990 (375 W, dual-RV970)
2. Radeon HD 6970 (250 W)
3. Radeon HD 6950 (200 W)
4. Radeon HD 6930 (186 W)
5. FirePro V7900 (150 W)
6. FirePro V5900 (75 W)