9800 Pros with the R350 cores don't. 9800 Pros with the R360 core do.
That's the 9800XT core, and many of the newer 9800 Pros have the R360. To
enable it, you have to reflash the BIOS with the appropriate and specific
9800XT BIOS for that manufacturer. This also gives you the higher
core/clock speeds as well. Without the reflash, the R360 core won't give
the signal.