It seems that the latest version of Rabit is able to edit not only 2D clock, but also 3D clocks now on X1*** cards. Changing the 2D speed to the same as the 3D speed can also come in handy for folders.
This is the standard ATI X1900XTX bios:
This is the Sapphire X1900XTX Toxic bios:
It looks like the Overdrive #2 profile holds the 3D speeds. The Default profile and Overdrive #1 profile seem to hold the 2D speeds.
The new Rabit can be downloaded here: http://www.techpowerup.com/downloads/283
Anybody willing to try this out? If it doesn't work, try enabling Overdrive in the ATI driver. I don't own an X1*** card, so I'm not sure if this option is still available with these cards......