[net.micro.pc] Running PC COM ports at 19.2K

kbb@faron.UUCP (Kenneth B. Bass) (09/10/85)

*** REPLACE THIS BUG WITH YOUR FIX ***

This is a warning to those of you who have been talking about
running your COM ports at 19.2K baud.

As you have probably already discovered, IBM does not state(explicitly)
that the ports will run at that rate (nor does it state the opposite).
If you go to the 8250 data sheet though, you can figure out how to get the
UART to go at 19.2K (ie, change the 16bit divisor).   I have done this
for my own communications applications, and it seems to work fine.

But BEWARE!!!!!!!

There may be a (good) reason why IBM doesn't mention this fact.  My
intuition tells me that when IBM designed the COM ports, they left
very little tolerance for running at high data rates, such as 19.2K.
I can't say what will happen when you run them at this rate, but
that is doing something with a machine that is not supported by the
manufacturer.

Like I said, I have run my PCs at 19.2K and up till now have had
no problems.  But I try to avoid that rate unless needed.  Why
flirt with trouble.


			"It ain't necessarily so"
			ken bass
			linus!faron!kbb