I have a Sapphire HD5850 Xtreme.  The BIOS limit on the core clock is 900 MHz.

With Catalyst 11.6 I can easily increase the clock frequency beyond 900 MHz but in Catalyst 11.4 I'm not able to.  (Catalyst 11.4 is quite a bit faster than Catalyst 11.6 for me).

To the person that can help me to clock my card significantly beyond 900 MHz while using Catalyst 11.4 without resorting to WINE/Windows/DOS/BIOS-flash I offer 1 BTC.  I'll settle for a new limit of 1150 MHz or more.