I think AMD has tweak some settings toward 7970.
Tested on Linux and ATi Radeon HD 5850. AMD APP SDK 2.7 in system with Catalyst 12.4 was installed manually. Cg Miner 2.4.1. Core Peak - 750 MHz, Memory Peak - 250 MHz.
Driver SDK Perfomance
12.1 2.6 301.9 Mh/s
12.4 2.7 298.5 Mh/s
11.11 2.5 307 Mh/s
I also use CGMiner. What kernel was this? Phatk? It was my impression that if you have to use 2.6 on a 58xx card, diablo was better than phatk.
The fact that it doesn't give amazing results on a 58xx cards doesn't surprise me, and it's kinda why I havn't upgraded myself. Anyone with a 7xxx card tried it out?