This is actually a generic ChibiOS question but I thought that I'd put it here so the SPC56x forum didn't look so lonely

How can one set the rate at which a thread is executed?
Example; In my code (using µC/OS-II) I have a 200Hz (highest priority), 100Hz (middle priority), and 10Hz (lowest priority) task. These threads need to execute at precisely these frequencies.
How would this be done in ChibiOS?
Kevin