What follows is a series of questions and answers about modems, which have been found to be of general interest. The answers to these questions have been drawn from various publicly available sources, as well as my own personal experience.
Q. What is a Winmodem1?
A. Winmodem_ is a registered trademark of 3Com, but generally refers to several varieties of "controllerless" or "software" modems. Some functions of these modems are performed by the system's CPU (Central Processing Unit), rather than by hardware within the modem. For some modems (controllerless modems) the CPU only performs minimal control functions for the modem, resulting in a modest increase in load, while in others (software modems) the CPU must handle DSP (Digital Signal Processing) functions, significantly increasing the load on the CPU. These modems also require a software "driver" before they will work at all and are generally tied to a single operating system. It is generally recommended that these modems only be used in fast (133MHz or faster) Pentium systems. Operating system upgrades can be problematic with these modems, as can other software that modifies your system.
Q. What does V.902 mean, and how does it relate to X2 and K56flex?
A. V.90 is an international standard set by the International Telecommunication Union (ITU) describing the technical specifications for 56K modems. V.90 merged the two major competing proposals for 56K modems, USR's X2 and Rockwell/Lucent's K56flex, but is not identical to either. V.90 provides for receive speeds up to 56 Kbps. Your actual speed depends on line conditions and interoperability issues. V.90 is an asymmetric protocol, where the "downstream" speed (from your Internet Service Provider, ISP, to your modem) may be up to 56Kbps, while the "upstream" speed (from your modem to your ISP) is limited to V.34 speeds (up to 33.6Kbps). Some modems may support both V.90 and X2, while others may support V.90 and K56flex. It is unlikely that you'll find a modem that supports all three.
Q. Why don't I get a 56K connection with my modem?
A. There is no easy answer to this question, because there are so many factors involved. Some of these are:
Q. My modem says "connected at 115200": is it really talking that fast?
A. Your modem is not really communicating with the other end at 115200 bps. Your system is reporting the speed at which it is talking to your computer, not the distant modem. The two primary causes are:
Q. I acquired a cheap modem that doesn't have a manufacturer's name. How do I find out who made it?
A. If your modem has a FCC ID number (they all should),
you may be able to look up the manufacturer on the FCC site:
The Navas 28800-56K Modem FAQ:
V.90 Frequently Asked Questions:
Curt's High Speed Modem Page:
3Com V.90 Technology White Paper: