Apple Performa 6400/180 - Manual (Page 37)

Basics Modems - 35
Modems
Some Performa 6400/180 and 6400/200 computers
shipped with internal GeoPort modems and some with
internal Global Village modems. If the modem isn’t replaced
like-for-like, the communications software is incompatible
with the modem.
To identify the modem originally shipped in the computer
look at the last three characters of the serial number to
compare with characters found in this table.
Modem 6400/180 6400/200
Global Village Platinum 7U7 836
GeoPort 95R 95S