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~m



  > From: "chefren" <chefren@pi.net>
  > Date: Fri, 8 May 1998 17:39:29 +0200
  > Subject: Re: BE/LE
  > ...
  > > Intel had proposed somnething like this for a really cheap
  > > mostly-software modem -- to which I thought "what a great
  > > idea. For Intel. Dump a $9 part, and use 80% of the
  > > CPU cycles of a $350 part."
  > 
  > Well that was a little overblown at that time from Mr
  > Grove and I think it still is. Nowadays there are 2-4
  > times faster CPU's. Within 2 generations those old 80%
  > will be less than 10%. Since most people use a modem not
  > all the time it will be about 1-5% of a $350 part in the
  > near furture. (Hehe... I observe lots of people that use
  > 40-80% of their CPU time for MP3 decoding and they have no
  > problems with the performance penalty!)
  > ...
  > Of course there is some weakening, I only try to state
  > that a 400MHz 32 or 64 bit CPU loses only one or two
  > 400 MHz cycles to do a BE/LE swap or align buffers. That's 
  > about 1/10 or less of one 33MHz PCI bus cycle.

The specific problem with the concept of "doing it in software"
.vs. "doing it in hardware" is in critical timing issues.

Your CPU can clock at 1,000 MHz, but if you're doing a modem and
sampling waveforms, it has to be real-time, it CAN'T be on
a as-time-is-needed basis.

Most/many do-it-in-software proposals I've seen seem to cost huge
amounts of CPU and/or elapsed time. For example, debouncing front
panel switches, multiplexing LCD lines, ...


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