Why with this bat i have only 400kh/s whit my r9 280x?
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
cgminer.exe --verbose --scrypt -o stratum+tcp://fry.minebig.com:3341 -u xxxxx -p xxxx --thread-concurrency 11200 -I 13 -g 2 -w 256 --gpu-engine 1080 --gpu-memclock 1500

What i must change?