Serial port problems on 6300

[Jerry Theisen]

I have an AT&T PC 6300 that has worked without a problem for 2 and a half
years.  Now for some reason, the serial port has up and died.
These are the symptoms:

	I hook up a modem (AT&T 4000) and an rs232 cable.
	I enter my communication program (ctrm).
	As I enter characters the transmit light on the modem blinks, but
	   nothing is echoed on the screen, and indeed the
	   receive light on the modem (those that have one) never
	   blinks.  And I cannot get the usual modem prompts.
	I hooked up the cable and modem to another 6300 and both work
	   fine (same settings of 1200 baud, 8 data bits, 1 stop bit,
		 no parity, and com1 as the port).
	I ran the customer diagnostics program and it says the serial
	   port is installed and working fine.

But if the serial port is fine, and the modem is fine, and the cable
is fine, then what could the problem be?  Since the modem and cable
work on other machines, I have to believe it's the port.

I tried installing another serial port, but can't get the 6300 to recognize
it.  Is there a dip switch somewhere that I set to tell the 6300 that
there are 2 serial ports installed?  If not, should it automatically
recognize the additional port?  Is there a way to simply disable the
primary port?

Thank you in advance for any help you can give me.

Jerry Theisen
attunix!jerry