To understand what is being asked for, it is necessary to understand how and modern modem works. Modems send signals down telephone lines which we all associate with the squeaks and hissing sounds which we hear when the modem starts, or if we pickup a phone on a line where a modem or fax is operating. At the other end the signal has to be turned back into ones and zeros again, which in early modems was done with electronic circuitry tuned to various frequencies. Effectively the modem found the ones and zeros in the signal like radio finding one station out of all the different radio signals reaching the antenna. As microprocessors became cheaper and faster, and everyone wanted faster modem speeds, modem makers changed to measuring the signal on the wire 8000 times a second and using a series of calculations to decide what the signal on the line was. That new way of working is what pushed modem speed from 1200 bits per second to 33000 or even 56000 bits per second. Inevitably the question eventually arose as to why the modem producers should buy a processor to do those calculations when the PC also could do them itself.
The chips used in modems were designed specially for signal processing, but the central processor of a PC is general purpose. To do the calculations needed took the first Pentium processors half their time, leaving only half the processing
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