The infrared port is setup by the 600's THINKPAD program, named TP2.EXE.
This setups all of the parts of a Thinkpad computer.
If you flash the BIOS with a newer BIOS, then all of these settings are
re-set to defaults. So one must re-run the TP2.EXE again to set the
The 600 can only run so many ports at one time, so for instance you may
have to disable the built-in COMM port, in order to be able to have an
IRQ for the Infrared Port. Etc. Disable the MIDI, Joystick, etc., so
that the infrared port can be used.
And the infrared port is operated by the DLL file, INFRARED.PDR, which
must be used.
For all of the info, open up the Thinkpad program, TP2.EXE, and click on
the Help icon, search for the word "infrared", and you'll find all that
you need to know. (s)