No clue.  If they're anything like the 6000 series chips, then no.  Well...  sort of.  With the 6000 series cards, you couldn't drop the memory clocks down lower than 125Mhz below the core clock.  If you were running at 1000Mhz, you couldn't go lower than 875 (etc).  You also couldn't adjust the voltage.  With the 5000's, the code in AMDOverdriveCtrl interacted directly with the hardware to change the voltage.

I ended up flashing the BIOS on all of my 6000 cards to custom clocks/voltages to get around the problem.  I'm not sure if a program came out since that will adjust them (in Linux).