Date: Wed, 10 Mar 1999 11:24:58 -0800 From: Darryl Okahata <darrylo@sr.hp.com> To: freebsd-hardware@FreeBSD.ORG Subject: Re: PCI WinModem Message-ID: <199903101924.LAA13771@mina.sr.hp.com> In-Reply-To: Your message of "Wed, 10 Mar 1999 13:45:16 EST." <Pine.BSF.4.10.9903101342390.43830-100000@picnic.mat.net>
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Chuck Robey <chuckr@mat.net> wrote:
> The simple minded thing just offloads all
> the signal processing of a modem onto your processor, which means it
> can't do anything else useful while the modem's going. That isn't
> smart, that's idiotic, especially seeing as the price of *real* modems
> isn't all that high, comparatively speaking.
I'm wondering: is this really how winmodems work? I've always
thought that this is how winmodems worked, but, after thinking about it,
they don't have to work this way. The DSP could be done by a cheap IC
(and often is, on non-winmodems, at least). That leaves the "com
port/external modem emulation hardware", which could be completely
dropped without affecting performance.
In a non-winmodem modem, you've got a processor that handles I/O
from the PC and the DSP -- something like:
+------------+ +-----+ +-----------+ +----+
| phone line |-->| DSP |-->| processor |-->| PC |
+------------+ +-----+ +-----------+ +----+
Now, for an internal modem, this processor is really superfluous. One
of its functions is to handle the various "AT" commands, but using the
PC for this is a fair trade-off for many people (as long as there's no
possibility of data loss with heavy loads).
I like offloading tasks from the CPU, and so I'd never buy a
winmodem, but winmodems might be adequate for some people (iff the DSP
functions were not done by the CPU).
--
Darryl Okahata
darrylo@sr.hp.com
DISCLAIMER: this message is the author's personal opinion and does not
constitute the support, opinion, or policy of Hewlett-Packard, or of the
little green men that have been following him all day.
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