From owner-freebsd-current  Thu Oct 31 11:04:25 1996
Return-Path: owner-current
Received: (from root@localhost)
          by freefall.freebsd.org (8.7.5/8.7.3) id LAA28238
          for current-outgoing; Thu, 31 Oct 1996 11:04:25 -0800 (PST)
Received: from phaeton.artisoft.com (phaeton.Artisoft.COM [198.17.250.211])
          by freefall.freebsd.org (8.7.5/8.7.3) with SMTP id LAA28230;
          Thu, 31 Oct 1996 11:04:23 -0800 (PST)
Received: (from terry@localhost) by phaeton.artisoft.com (8.6.11/8.6.9) id LAA25769; Thu, 31 Oct 1996 11:56:39 -0700
From: Terry Lambert <terry@lambert.org>
Message-Id: <199610311856.LAA25769@phaeton.artisoft.com>
Subject: Re: Any ISDN-BRI cards work under FreeBSD?
To: kuku@gilberto.physik.rwth-aachen.de
Date: Thu, 31 Oct 1996 11:56:39 -0700 (MST)
Cc: gjennejohn@frt.dec.com, questions@freebsd.org, current@freebsd.org,
        isdn@muc.ditec.de
In-Reply-To: <199610311454.PAA05342@gilberto.physik.rwth-aachen.de> from "Christoph Kukulies" at Oct 31, 96 03:54:32 pm
X-Mailer: ELM [version 2.4 PL24]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-current@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

> > > done it yet.  They currently only run single channel connections (you
> > > can have two different connections to different destinations).  The
> > > theoretical maximum throughput is 8 kB/s (64,000 bps), which is
> > > somewhat less than the theoretical maximum of the 115.2 kbps lines
> > > (11.52 kB/s).
> 
> Why do you divide by 8 in the one case and by 10 in the other?

My guesses:

8)	8*8k = 64k; conversion is for sync framing

10)	1 start + 8bits + 1 stop = 10bits; conversion is for
	async framing

A more interesting question might be 64k + 64k = 128k.  128k != 115.2k.
Here the answer is that the max PC port rate is 115.2k (unless you
get a decent [non-Intel] UART serial board or buy a card from Dennis).

So the conversion from sync to async is internal to the device, and
is limited by the bit rate of the device-to-computer interface.

This is the general problem with externally interfaced serial devices.


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.