> > instead of an interrupt per character...Just a thought....
> 
> Err.. AFAIK, the winmodems use the system CPU for a DSP, so they require
> relatively much processing power.  I don't know if I'm correct, but I
> would guess that the winmodems have only A/D and D/A converters with FIFOs
> and the system CPU has to analyze the sampled waveforms and produce output
> waveforms (this is done by a dedicated DSP chip in "real" modems).

there are two kind of these shitty hardware. there are software winmodems
as you say, and there are normal true modems but without serial-like
interface. it is a good idea not to implement this hardware because it's
not needed on internal boards, but the problem is in lack of
specifications. each winmodem need to have separate driver.