Subject: Re: Baudrates not what they used to be?
To: Allen Briggs <briggs@puma.bevd.blacksburg.va.us>
From: Bill Studenmund <wrstuden@loki.stanford.edu>
List: port-mac68k
Date: 11/15/1995 11:17:06
> 
> > has anybody using a Mac IIci/si/vi/vx noticed that using a baud rate
> > of 9600 baud or lower doesn't work with the last changes in the
> > serial driver code?
> 
> Has anyone noticed this on a IIci, specifically.  It looks like the
> si/vi/vx are currently broken.

A simpler test (if you have 2 computers) is to connect a mac IIci running
the new kernel to a computer using a known-good terminal program. Like
a terminal emulator running under MacOS or DOS or NetBSD on a II, IIx,IIcx.

A mac-to-Deskwriter cable will work for the connection.

Try stty -f /dev/tty00 X to set the baud rate to X. Set the terminal
emulator to 9600. "echo hello > /dev/tty00" will send stuff out the
modem port. If the characters show up right at 9600, the IIci is ok.
If you need to set the baud rate to 10200 to get characters to show
up right, then the IIci value is wrong.

Could someone with a IIci try either this experiment or the one Walter
suggested?

> > Does anybody know where this sccClkConst of 122400 for
> > MacIIci/si/vi/vx comes from
> 
> I think it was determined experimentally for the IIci and we assumed
> that it would be correct for other machines.  Since I hadn't heard
> anything, I assumed it was working...

The thing that puzzles me is that this clock is used to generate LocalTalk
packets. A 6% error here would totally mess things up (since there is no
divisor factor used for them). :-(

Take care,

Bill.