Initially the solution was to use LSI ASICs which shrank the various implementations into a small number of components, but since standards continued to change, there was a desire to create modems that could be upgraded. Finally, compatibility with older protocols using completely different modulation schemes would have required a modem made with discrete electronics to contain multiple complete implementations. This made the construction of a mainly analog/discrete component modem impossible. Later techniques used in modern V.34, V.90 and V.92 protocols (such as a 1664-point QAM constellation) are so complex that implementing them with discrete components or general purpose ICs became impractical.įurthermore, improved compression and error correction schemes were introduced in the newest protocols, requiring extra processing power in the modem itself. New modulation required mixing analog and digital components, and eventually incorporating multiple integrated circuits (ICs) such as logical gates, PLLs and microcontrollers. Under these conditions, modems could be built with the analog discrete component technology used during the late 70s and early 80s.Īs more sophisticated transmission schemes were devised, the circuits grew in complexity substantially. The first generations of hardware modems (including acoustic couplers) and their protocols used relatively simple modulation techniques such as FSK or ASK at low speeds. The audio signals to be transmitted must be computed on a tight interval (on the order of every 5 or 10 milliseconds) they cannot be computed in advance, and they cannot be late or the receiving modem will lose synchronization. Softmodems are sometimes used as an example of a hard real-time system. By analogy, a linmodem is a softmodem that can run on Linux. Softmodems are also sometimes called winmodems due to limited support for platforms other than Windows. A PCI softmodem (left) next to a conventional ISA hardware modem (right)Ī software modem, commonly referred to as a softmodem, is a modem with minimal hardware that uses software running on the host computer, and the computer's resources (especially the central processing unit, random access memory, and sometimes audio processing), in place of the hardware in a conventional modem.
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