postscript printer, installation help?

[Rob Farlee]

How do I install a Postscript printer on a Personal Iris?

I plugged an HP Laserjet III into the parallel port of a 4D20, used the
printer tool to configure it as a "generic printer", and it prints text
files just fine. 
How do I configure the Iris so I can plug in the HP Postscript cartridge
and get text and pictures, instead of garbage, out?  After an hour search, 
no where in the manuals can I find a jot of information about postscript
printing, except buried deep in documentation of the printfile filters. 

Background: please forgive me if this is a dumb question which may have 
been answered on the net in the past, as I am but a novice to the Iris. 
I'm running IRIX 3.2; SG hasn't sent me 3.3 yet. 
I checked out the laserprinter (after installation of the postscript
cartridge, 5M total printer memory, using the parallel port) on a PC, so
know there is no problem with the hardware.
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