This is a good little article from GVC Canada's site. I thought it would be useful for people woh want
to know why software modems are cheaper, and thus usually not as good.. Remember you get what you pay
Explaining GVC's 56K Modems
To better understand the variety of 56K modems being sold today you need some understanding of how a
modem works. Essentially the modem can be broken down into three primary functions:
MCU (Micro Controller Unit): This contains the AT command set (for controlling the modem);
data compression (V.42bis, MNP5); data correction (V.42); fax capability etc.
DPU (Data Pump Unit): Modulation; echo cancellation etc. Essentially converting digital signals
to and from analog signals.
DAA (Data Access Arrangement): Physical interface to POTS (Plain Old Telephone System).
Controller, controller-less and software modems are differentiated by how they handle these functions
whether the modem hardware does the work or it is off-loaded to the computers cpu). Off-loading work to
the cpu will result in slowing down the computer.
Controller modem: The MCU, DPU and DAA functions are all controlled by the modem hardware.
Controller-less modem: Only the DPU and DAA functions are controlled by the modem hardware. The
primary advantage to a controller-less modem over a controller modem is the ease of upgrading (driver
issue) and the lower cost. The disadvantage being the utilization of the cpu.
Softmodem or Software modem: Only the DAA function is controlled by the modem hardware. The
primary advantage to the software modem is a lower cost again ? of course the downside is more cpu