setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
microcoinminer.exe -o x -u x -p x --scrypt --Nfmin 4 --Nfmax 30 --StartT 1389028879 --queue 0 --scan-time 2 --expiry 4 -g 1 -w 256 -I 12 --gpu-engine 1125 --gpu-memclock 1250 --thread-concurrency 35000
If you used the latest thirtybird yacminer release instead of microcoinminer and used its advanced options you should get 50-60kh/s reliably from a 7950.