from abit's site:  
CPU
Supports AMD Athlon/Duron 600MHZ-1.2GHZ 200/266MHz FSB Socket A Processors 
but per their email:
Dear Customer,
Sorry, KT7-RAID can only support Duron up to 950Mhz with the latest bios.
Morgan core Duron is not supported.
I think you can run a faster Duron but it is just not official supported.  Does anyone run faster than a 950 Duron on their kt7?