Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!hayes!tnixon
From: tnixon@hayes.uucp
Newsgroups: comp.dcom.modems
Subject: Re: Clarification on MNP4 and Everex 24+
Message-ID: <3794.27c52a5c@hayes.uucp>
Date: 22 Feb 91 14:27:40 GMT
References: <6831.27C20BB1@zswamp.fidonet.org>
Organization: Hayes Microcomputer Products, Norcross, GA
Lines: 23

In article <6831.27C20BB1@zswamp.fidonet.org>,
root@zswamp.fidonet.org (Geoffrey Welsh) writes: 

>    BTW, I would have thought that 256 bytes was not enough to allow decent 
> MNP5 and V.42bis data compression.  Am I really misunderstanding the process 
> by a large margin?

Yes, you are.  The size of the DTE buffer has nothing to do with the 
amount of memory available for V.42bis dictionaries.  Most modems 
provide room for at least 1,024 nodes [roughly 16K RAM], and many 
(including Ultra 96) provide for 2,048 nodes [roughly 32K RAM].  The
minimum allowed by the standard is 512 nodes. There is very little
performance improvement, and risk of performance DECREASE, from
using more than 2K nodes in V.42bis.  The amount of memory required
by MNP5 is fixed, about 1.5K RAM.   None of these figures have 
anything to do with the size of the circular buffer used for 
transferring data to/from the PC.

-- 
Toby Nixon, Principal Engineer    | Voice   +1-404-840-9200  Telex 151243420
Hayes Microcomputer Products Inc. | Fax     +1-404-447-0178  CIS   70271,404
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