2.6 Software-based Modems (winmodems, linmodems)
Introduction to software modems (winmodems)
Software modems turn over some (or even almost all) of the work of the modem to the main processor (CPU) chip of your computer (such as a Pentium chip). This requires special software (a modem driver) to do the job. Until late 1999, such software was released only for MS Windows and wouldn't work with Linux. Even worse was that the maker of the modem kept the interface to the modem secret so that no one could write a Linux driver for it (even though a few volunteers were willing to write Linux drivers).
But things have improved some since then so that today (late 2001) many such modems do have a linux driver. There is no standard interface so that different brands/models of software-modems need different drivers (unless the different brands/models happen to use the same chipset internally). But some drivers may not work perfectly nor have all the features that a MS Windows driver has.
Another name for a software modem (used by MS) is "driver-based modem". The conventional hardware-based modem (that works with Linux) doesn't need a modem driver (but does use the Linux serial driver) After about mid-1998 most new internal modems were software modems.
Software modems fall into 2 categories: linmodems and winmodems. Winmodems will only work under MS Windows. Linmodems will work under Linux. They formerly were mostly winmodems so some also call them "winmodems". The term "Winmodem" is also a trademark for a certain model of "winmodem" but that's not the meaning of it in this document.
Linmodems
In late 1999, two software-based modems appeared that could work under Linux and were thus called "linmodems". Lucent Technologies (LT) unofficially released a Linux binary-only code to support most of its PCI modems. PC-TEL (includes "Zoltrix") introduced a new software-based modem for Linux. After that, interest increased for getting winmodems to work under linux. There is a GPL'ed driver for Intel's (Modem Silicon Operations) MD563x HaM chipset (nee Ambient division of Cirrus Logic). As of mid-2001 there are also drivers for: Conexant HSF and HCF, Motorola SM56 (support terminated), ESS (ISA only), and IBM's Mwave for Thinkpads 600+. See http://linmodems.org.
What percent of software modems now (2001) work under Linux? Well, there's a number of modem chips not supported: Lucent/Agere ARM (Scorpio), 3COM/US Robotics, some SmartLink (3 different chipsets), Ambient HSP, and possibly others. So it seems that over half the software modem chips were supported as of late 2001. As of 2005 it seems that the situation hasn't improved and may even have deteriorated some. Why? Well, Linux on the Desktop didn't grow as fast as expected and many PC users went for higher speed cable modems and DSL.
There's also the problem that many of the drivers will only work with older versions of the Linux kernels.
Be warned in advance that determining if your modem is a linmodem may not be easy. You may need to first find out what chipset you have and who makes it. Just knowing the brand and model number of your modem may not be sufficient. One method is to download the scanModem tool from http://linmodems.org but the results may be hard to decipher and you may need to ask for help from the linmodems mailing list. Another way to find this out using say "lspci -v" and then looking up the chip maker using the long modem number. This requires checking a database or searching the Internet. Still another way is to look at the fine print on the chips on the modem card. All this is not always simple. It could happen that you will put a lot of effort into this only to get the bad news that your modem isn't supported. But even if it is supported, support may only be for an old version of the kernel. See Linmodem-HOWTO for more details.
Linmodem sites and documentation
- Linmodem-HOWTO
- Winmodems-and-Linux-HOWTO (not as well written as Linmodem-HOWTO)
* License
