Re: IIgs builtin serial and a Performa Modem Project

["Henry Broekhuyse" <broekh@unixg.ubc.ca>]

The "extra" ninth pin was used, as you correctly identified, to provide
power on the "Geoport" serial port.

You may be interested in this web page, with instructions on modifying this
modem for use with 8-pin serial ports:
http://members.aol.com/lockjaw8y9/gvtpg2p.html

Indidentally, while looking this up I discovered that unlike most modems
sold for the Macintosh market the TelePort Gold II modem performs error
control and data compression in software, rather than in the modem's
hardware (chip set).