Well......first off look at the PARALLAX extended OPCPDE list at this link:

http://www.dontronics.com/psbpix/chart.html

You can find out some information here:

http://www.dontronics.com/see.html

You can check out the Parallax web site for some information. I do not believe they still sell the tools they once had for working with the early PICs. Here is the PARALLAX web link.

http://www.parallax.com/index.asp

Some information about a free assembler and simulator for PICs canbe seen here:

http://gputils.sourceforge.net/
http://www.dattalo.com/gnupic/gpsim.html

I do not actually know where you can download the PASM.EXE file or the PSIM.EXE file for the early PARALAX assembler and simulator tools but you could check here....

http://margo.student.utwente.nl/el/micros/pic/

Or you could try to put PASM.EXE or PSIM.EXE into Google to see what you might find.

Michael Karas