> I think I know why the zs chips are normally run with a X16 clock
> divisor.  But is there any reason why they shouldn't run X1 if userland
> requests a baudrate that can be achieved that way but not with X16?

There shouldn't be.

The main advantage you get from deliberately using X16 mode is that the
input logic can use the extra ticks to clean up an input signal by taking
multiple samples and integrating them -- at least one motorola serial chip
(68681?) does this, but I no longer recall offhand if the 8530 did it too.

Todd Whitesel
toddpw @ best.com