> 	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?
why? 2400/10=240. i don't know how netbsd handles serial port on sparc,
but with low speed i think serial port sends one interrupt per character.
so why it shouldn't work?