There are at least three types of controller-based PCI modems:

Lucent Venus chipset:
   Multitech MT5634ZPX-PCI,
   Actiontec PCI56012 (IBM 33L4618 or GVC MD0223)

USR/TI Kermit chipset:
   the 3Com/USR 3CP5610 family, which includes models 5613, 5609, and OEM models 2976, 2977, and 3258

TOPIC TP560i chipset:
   Zoom 2920 (Digitan DS550-558),
   Well Communications FM-56PCI-TP (GVC MD0321), and
   Archtek Smartlink 5634PCV.

information from:
http://www.idir.net/~gromitkc/winmodem.html
also try linmodem.org
the serial howto
the modem howto