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From: billsey!nesbbx@agora.UUCP (Bill Seymour)
Newsgroups: comp.sys.amiga.datacomm
Subject: Re: What's the difference between a Supra MNP and MNP-plus?
Message-ID: <192260b4.ARN00ad@nesbbx.UUCP>
Date: 13 May 91 22:16:20 GMT
References: <1991May10.233030.22425@ichips.intel.com>
Reply-To: billsey@nesbbx.UUCP
Followup-To: comp.sys.amiga.datacomm
Organization: NES, Inc.
Lines: 45

In article <1991May10.233030.22425@ichips.intel.com>, Mark Waggoner writes:

> Could someone tell me what the difference between a Supra 2500 MNP
> and Supra 2400 MNP plus is?  

	The MNP does regular 3/12/2400 baud operation, plus adds MNP levels
2-4 error correction and MNP5 data compression.  When connected with another
MNP compatible modem, you should see an improvement in error handling and
an improvement is uncomressed data speed. The theoretical limit to the higher
throughput is 4800 baud, or a 2:1 ratio. In the real world, expect to see
about 3000 baud for text and something less than 2400 baud for compressed
data. 
	The Plus modem has everything the MNP does, plus V.42 error correction
and V.42bis data compression. Both V.42 and V.42bis are more advanced
techniques than the older MNP stuff. V.42bis gives a maximum compression
ratio of 4:1, making 9600 baud theoretically possible. But there's a difference
on precompressed files... With MNP5, you get an actual *slowdown* on
precompressed files, since it doesn't know enough to shut itself off,
with V.42bis, the compression algorythm shuts itself down on compressed files
yet still gives you the advantage of the psuedosyncronous transmission
(start and stop bits are stripped, giving a 20% speed increase) Because of
this, you should see data rates of about 5000 bps with text and 2800 bps
on compressed files.

> I'm not fully conversent on protocols, compression schemes and error 
> correction.  My local sysadmin recommends:
>   2400 baud with V.22bis with MNP2-4 for error correction and MNP-5 for
>   data compression.  

	You'll get that with either modem, although if you're transfering
compressed files, you'll want to disable the MNP5.
 
> Will I get all of this with the Supra?  Any other recommendations?
> 
> Thanks
> 
> --
> Mark Waggoner           waggoner@ichips.intel.com         (503) 696-4590
>                        No, I don't speak for intel.

	Bill Seymour	   (Is this really getting out beyond my machine?)
  -Bill Seymour     nesbbx!billsey@agora.uucp or nesbbx!billsey@agora.rain.com
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