I use GUIMiner with my 5830....
STOCK GPU (840) / STOCK MEMORY (1125)
OpenCL NONDEDICATED..I get 199 Mhash/s
Phoenix DEDICATED........I get 235 Mhash/s
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OVERCLOCKED GPU (900) / UNDERCLOCKED MEMORY (900)
Using the following flags:
-k phatk DEVICE=0 VECTORS BFI_INT WORKSIZE=256 AGGRESSION=13 FASTLOOP=false
Phoenix DEDICATED.......I get 280 Mhash/s
I tried MSI Afterburner - it was good, allowed me to overclock and underclock etc - but also caused some blue screens. Also after using it, I noticed the GPU/Memory figures in the ATI CCC didn't match what was showing in Afterburner. So I switched back to just using ATI CCC - I may lose a few Mhash/s but the PC doesn't crash and the temps are slightly lower.