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From: Robert Shady <rls@server.id.net>
Message-Id: <199602231332.IAA06064@server.id.net>
Subject: Re: ISDN Questions
To: gjennejohn@frt.dec.com
Date: Fri, 23 Feb 1996 08:32:39 -0500 (EST)
Cc: peter%thirdeye.com@inet-gw-1.pa.dec.com,
        freebsd-hardware%freebsd.org@inet-gw-1.pa.dec.com
In-Reply-To: <9602231154.AA00568@cssmuc.frt.dec.com> from "garyj@frt.dec.com" at Feb 23, 96 12:54:45 pm
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> > A couple of questions about ISDN and FreeBsd.
> > 
> > 2.  Has anyone done anything that will work with the
> >     Motorola BitSurfer Pro?
> 
> not that I know of.

The BitSurfer PRO wouldn't need anything dependant on the kernel.  Just drop
it in & treat it like a modem, run PPP to your provider & everything should
be fine.

> > 3.  What are the advantages of a card over an external box?
> >     Interrupt rate? Feature control?
> 
> with a card you get the full B-channel speed (64 K/sec, 128 K/sec with
> channel bundling). Unless you have a really fast serial port (> 115.2)
> you can't get the full speed when you use channel bundling with an
> external device. Note that the II stuff doesn't currently support
> channel bundling, though, so this point is moot.

The other advantage of a card vs. an external device is that with an internal
card, you are talking to it in Syncronous mode, which simply means you send 
a byte, it sends 8 bits.  An external device talks in Asynchronous mode,
which simply means you send a byte, it sends 10-11 bits.  Right off the bat,
this means you will get an approximate 20% loss of throughput with an
Asyncronous device Vs. a Synchronous device...  Now, you through in the fact
that most external Asynchronous devices have to do the Asynch->Sync conversion
"on-the-fly", it's possible you may loose a little more than that.

	-- Rob
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