I got to testing the fifo overrun problem a little, and there is no problem
   at 19.2, but there is at 38400.  I'd like to try values in between, but
   tcsetattr won't permit them. Is there a reason why it has to be this way?
   Seems like 28.8 and 33.whatever should be allowed too.


funny, i was looking at this recently...


from sys/arch/sparc/dev/zs.c:zs_set_speed():

        /* XXX - Allow some tolerance here? */
	if (real_bps != bps)
		return (EINVAL);


basically, the chip only supports certain values, and the current driver
will reject speeds not allowed, rather than just fudging it by actually
setting the speed to the real value.