Software Modems
Software modems
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Software Modems

Software modems

There are basically two types of modems available, traditional hardware based modems and software based modems. Software modems have fewer chips on board, the tasks that would have been done by the missings chips are transferred to the host computer's main processor (the Pentium, etc..).

Two functions performed by any modem are:

  • Modem datapump functions - the basic modulation/demodulation functions.
  • Modem control functions - hardware error correction, hardware compression, AT command interpretation.

US Robotics (now 3Com) manufactured Winmodems still have the datapump chip, but modem control functions are done by the host computer's main processor. This slightly adds to the load on the main processor. These modems are popular as OEM products, so when you buy a new PC, chances are that your modem is winmodem.

Picture of a modem chip - 7KHSP modems (Host Signal Processing), transfer both datapump and modem control functions to the host computer's main processor. This greatly adds to the load on the main processor, which may be minimal on a 300MHz Pentium II, but, really slows down a Pentium 133.


  • Cost - software modems are cheaper to manufacture.
  • Size - with less chips required, software modems can be integrated on the computer motherboard, ideal for laptop computers.
  • Easily upgraded.


  • Requires a fast processor - the faster the better.
  • Connection speed can depend on processor speed - 28.8 or 33.6Kbps may be marginal on a Pentium 100.
  • Disconnections can be a problem if system resources are low. For example, using more than 256 colour resolution can cause disconnection due to competition with the videocard for bus resources.

Danny Fye, who has experimented with various types of modems writes:

"I just achieved a milestone for me. I got a throughput of 6010 cps. A throughput of a connection speed of greater than 52000 bps.
I have used these silly winmodems with mediocre results of much less and always wished I could see something more like what a 56k modem should fully be capable of.
I got me an external U.S. Robotics modem and put it on the serial port and now real speed is finally a reality. I am using Worldnet with Windows Me. I did myself a favor and did a screen capture. The dun says I have a connection speed of 50,666.
USB type modems can be operated in pretty much the same way as a "winmodem." So one should not assume that just because they have a USB modem that they will get the full performance. I know better because I had one and it worked very poorly. Even so, the brand of modem can also make a big difference. I had an external Zoom and it was good, but the external U.S. Robotics is downright excellent!"

Dannys's experience with USB modems echoes my own. Recently, a friend who had been having connection problems with a software modem, ask me to setup the replacement - a USB modem. Comparison of connection speed and throughput between the two modems showed that although the USB modem reported a higher initial connection speed, its throughput was noticeably lower.

In conclusion, software modems tend to be unreliable. A hardware modem offers more performance and reliability.

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