The following results have been achieved:
http://imageshack.us/a/img266/5644/7970reapertests.pngThe best config for 7970 is (565khash\s):
worksize 256
vectors 1
aggression 13
threads_per_gpu 1
sharethreads 32
lookup_gap 2
gpu_thread_concurrency 34816
Maybe I will continue experiments to find the better config. But it seems that 7970 is better for BTC mining because it is not hard to get ~700mhash\s
