Here's the quick way to the Chainsaw.

Start DOOM 1.1 with the following command line:

DOOM -DEVPARM -SKILL 4

At the opening screen, type the following:

iddqd (ENTER not required.  His eyes turn glassy. This starts God
mode)

idkfa (ENTER not required. Gives you ammo and all weapons.)

1 (ENTER not required. This switches to chainsaw)

Sincerest thanks to those previously posting the basis codes!!