When using modem compression, the data is fed over the serial link (yes,
even an internal modem appears as a serial device) uncompressed, and as
such takes additional processor time (this is PIO - slow and
CPU-intensive). The CPU is interrupted more often to pick up and deliver
data to the serial port, and a missed pickup can cause data
loss/corruption.
When using software compression, the data is fed over the serial port
*still compressed*, reducing the actual data transfer requirements at the
serial port. This lowers the CPU involvement in serial data transfers.
The trade-off is that the CPU must perform data compression, however this
it can do locally using very little CPU horepower (and do it at CPU
speeds!).
Steve Bourne
Technical Trainer
Lucent RABU
-----Original Message-----
From: Jake Messinger [SMTP:jake@ams.com]
Sent: Thursday, May 21, 1998 7:47 AM
To: Brantley Jones
Cc: Josh Richards; portmaster-users@livingston.com
Subject: Re: (PM) STAC Cards
On Wed, 20 May 1998, Brantley Jones wrote:
> Would there be any point in this, though? Would you get that much better
> compression ratios out of STAC as opposed to V.42 bis?
Think about it. V.42 bis compression is a function of the processor in a
modem. Stac compression would be a function of your processor on your main
board, in some cases, a 400 Mhz Pentium II. Plus stac is newer
algorhithms. What do you think? Ive heard a 20% average increase in
performance.
~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~
Jake Messinger ph:713-772-6690 Lucent Dealer
AMS, Inc. fx:713-774-3498 Medical Billing
8300 Bissonnet #400 jake@ams.com Internet Services
Houston, Texas 77074 www.ams.com/~jake Business Management
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