Follow the link I posted here:
http://www.pocketpcthoughts.com/foru...pic.php?t=7871
The application posted on the site (a link to the site is found in thread linked to above) on the left site, called "Speed Stepper" or something, that lets you toggle thru the various clock-speeds. I think there's a version, a little down the page, that is for 400 MHz XScale devices .