Well, according to AMD, if You press WIN+Break(or Pause) while idling on the desktop, You should be able to see less-than-rated clock speed on the "System Properties" page. Here's
a PDF from AMD, scroll down to the last page.
The driver might not be installed, but the board could still support Cool 'n' Quiet. So You should also check the info on page nine to see if the driver is installed or not.
Oh, and do note that the newer revisions of the A64 (CG core) run at 1000 MHz lowest, while the old ones run at 800 MHz. Despite the difference in clock speeds, 1000 MHz one runs ~10 Watts cooler than the old 800 MHz one because of lower voltage.