Mike Watson <PICLIST@MITVMA.MIT.EDU> wrote:

> I have a need to operate 3 comm ports on my pc .... but in use,
> com3 stops com1 working and com4 stops com2.
>
> It must (surely) be possible to configure the system so that I can
> use at least three of the ports at the same time.

Mike:

By default, COM1 and COM3 use IRQ4, and COM2 and COM4 use IRQ3.

To use three ports simultaneously, you need to assign each port a
unique IRQ... The most-common arrangement is COM1 = IRQ4, COM2 =
IRQ3, COM3 = IRQ5.

Of course, IRQ5 is the default interrupt for the second LPT port, so
if you have two printers, you'll need to assign COM3 to some OTHER
interrupt... It can get complicated, although the difficulty can
sometimes be eased by using a serial card that supports IRQ10-15.

-Andy

=== Andrew Warren - fastfwd@ix.netcom.com
=== Fast Forward Engineering - Vista, California
=== http://www.geocities.com/SiliconValley/2499