Software Modems

"Software Modems" (or "Soft Modems" as they are sometimes called) are modems which transfer many or most of the modem functions to software which uses your PC's CPU rather than performing them within the modem itself. This allows the manufacturer to produce a modem with very few parts on it (a HSP modem is little more than a host interface card and an associated modem software program), which greatly reduces their cost. It also allows some modem upgrades via software downloads rather than requiring firmware upgrades. In the early days of this type of modem, many users experienced substantial problems. In the last couple of years, however, many of these modems work well. This is a result of better modem drivers and the increased power of today's PCs.

Modems consist of two major components: 1) A datapump which performs the basic modulation/ demodulation tasks for which modems are named, and 2) A controller which provides the modem's identity: this is where the protocols for hardware error correction, hardware data compression, and basic modulation protocols (such as V.34, V.90, and V.92) exist. The controller is also responsible for interpreting AT commands.

A traditional modem implements both features in hardware (as chips inside the modem). A "controllerless" modem, such as the older USR Winmodem and a number of name-brand newer modems, still has a hardware datapump onboard, and just implements the controller functions in software running on your PC. However, a HSP (Host Signal Processor) modem dispenses with both the controller and the datapump, and uses software to provide both functions. That is, a HSP modems transfer the work normally done by the missing modem chips to software running your PC, which puts a considerable extra load on you CPU. All software based modems are operating-system dependent, so they may quit working when you upgrade your operating system. No software based modems will run under DOS, and I am unaware of any that will run under Unix and other operating systems.

However, soft modems have some real benefits in small devices such as laptop and hand held computers. They weigh less than traditional modems and take up less space. They also consume less electricity, which makes them ideal for battery-powered devices.

If you get a soft modem, I recommend staying away from El Cheapo "HSP" (host signal processing) modems because of the heavy load HSP modems place on your CPU. As mentioned above, the next level up of soft modems include an onboard Datapump, which relieves a substantial processing load from your PC. In summary, I recommend that if you are going to get a soft modem, spend just a little more for one with an onboard Datapump -- especially if you frequently run other processor-intensive applications such as a software DVD Player and action games.

Just as with hardware modems, when buying a soft modem your best choice is always to buy a brand name modem with good online support so that you will be able to get upgraded drivers when necessary (for example, when you upgrade your version of Windows). However, another line of thought is that some soft modems are now so inexpensive that they are considered "throw-away technology" -- you just throw them away if they quit working when you upgrade your operating system. See below for how to tell the difference in soft modems when you buy.