Btw I'm able to get ~200 MHash/s with my 5770 and about 170 without overclock using Guiminer. Just use extra flags: -v -w256
I get those same kind of numbers using -v -w128. I thought it was a model wide setting. All I've been seeing is for all 5xxx, and 6xxx to use -w128 for best performance. Maybe it's dependent on other system variables! 