Default clock speeds were listed as 378MHz / 351MHz. I believe the standard clock speeds for the Radeon 9800 Pro are 380MHz / 340MHz.
Was able to run at 439MHz / 383MHz before artifacts appeared in the UT2003 Flyby benchmark. Had to throttle down to 414MHz / 374MHz to complete all four 3DMark03 game tests without artifacts showing up.
First result is at 378MHz / 351 MHz. Second result is at 414MHz / 374MHz.
1280x1024 - from 147 fps to 155 fps
1600x1200 - from 106 fps to 116 fps
GT1 - from 171.9 fps to 176.0 fps
GT2 - from 37.7 fps to 40.9 fps
GT3 - from 33.5 fps to 35.8 fps
GT4 - from 33.0 fps to 36.0 fps
Overall - from 5501 to 5876