COMSET
By David Macchia

Comset will install com ports 3 and 4 in the DOS bios area
for IBM PC, XT, AT's and compatibles. The power on self tests on
these machines only tests for the presence of the first two
serial ports, and as a result any program which uses DOS
functions cannot access ports 3 and 4. DOS versions 3.3 and
above supports COM3 and COM4 as devices, and after using comset
you may use the MODE command and redirection of output to these
ports.

Most programs which support COM3 and COM4 do so by using the
actual device addresses rather than the DOS function calls.
However those which go thru DOS cannot "see" ports 3 and 4.
Many programs will not allow selection of any port above COM2.
To get around this there are a couple of companion programs
included with this package which will swap the com ports in the
DOS bios area. They are called COMSWPxy.COM, where x and y are
the ports which are swapped (ie: COMSWP14.COM will exchange ports
1 and 4).

Swapping the ports will allow you to access these ports, but
will not affect the use of them by direct access programs. For
instance I have my modem installed as COM4 and have swapped it
with COM1. Sidekick and Async are configured as COM1, while
Procomm and Xtalk are still configured as COM4. My mouse is
actually connected to the physical COM1, and uses direct access
so is configured as COM1. This may sound complicated, but I just
COMSET and COMSWAP14 in my autoexec.bat file and everything
works.

A few notes:

1) Physical ports 1 and 3, use the same interrupt as do 2 and
4. If you are using a mouse on one of the ports you probably
will not be able to run a communications program on the
other as the are both usually interrupt driven.

2) Using Sidekick's dialer may require the use of the public
domain program called SKFIX.COM, which is available on most
bulletin boards, to fool Sidekick into thinking DSR is high.
If you are using version 1.52 you may find you will need to
patch out address xxxx:8BB6 from 74 F0 to 90 90. This
worked for me, and really has nothing do do with comset.
SKFIX will also allow you to send stuff to your modem
through DOS redirection such as "TYPE SETUP.TXT > COM4:" to
send the contents of setup.txt to the modem even if DSR is
low.