>On VxWorks PowerPC, 100 microseconds (I think).

I'm not sure what exactly the figures you've quoted here are. For reference,
using Green Hills Ada, VxWorks and PowerPC we have an Ada.Real_Time resolution
of 16.67ms. If we link in to the sysAuxClk... we can get it to interrupt us ever
millisecond. I think I tried to make it every 100us but the setup operation
failed.

John