I have a program that wants to be woken up at 240Hz.  Since I'm doing
	this on a SPARC, whose clock interrupts at only 100Hz, I connected a
	loopback connector to one of the serial lines, set it to 2400bps, and
	then started dumping characters at it.  Of course, they came back at
	240Hz, just as I wanted.

I'm surprized that works.  Are you sure you're getting 240Hz wakeups?

Anyway, it might be more profitable in the long run to increase the
kernel clockrate.

Eduardo