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From: kjh@pollux.usc.edu (Kenneth J. Hendrickson)
Newsgroups: comp.dcom.modems
Subject: review of Practical Peripherals 9600SA
Message-ID: <28545@usc>
Date: 1 Dec 90 06:24:07 GMT
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Organization: EE-Systems, USC, Los Angeles
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I recently ordered a Practical Peripherals 9600SA modem from a mail
order house on the east coast.  Since they were out of stock, and since
a local company had a policy of 100% refund for any reason within 30
days, I decided to go get one there and try it out.

Initially, I was very pleased.  It was plug and play.  It supports V.32,
V.42, V.42bis, MNP2-4, and MNP5.  I had no difficulty at all dialing up
the University's V.32 modems (MNP5).  9600 bps was sure a lot nicer than
2400 bps.  I played with the registers allowing Data Compression and
Error Correction.  I found that _disallowing_ Data Compression yielded
higher data transfer rates!  This was true both for compressed files
(.ZIP) and for text files.  This was suprising, especially in the case
of text files.

Then I tried to call the University's 2400 bps modems using the 9600SA.
I experienced lots of noise problems.  I couldn't get a connection.  I
RTFM, and RTFM some more.  I played with many of the S registers.
Still, the noise problems existed.  Since I had experienced some noise
problems before with my 2400 bps modem, I got out my 2400 bps modem
again to see what it would do.  It worked just fine.  Trying the 9600SA
again showed it couldn't handle the connection at all.  I switched the
modems 4 or 5 times within a time period of about 1 hour, and each time
the 2400 bps modem worked just fine, while the PPI 9600SA couldn't hold
the carrier.  I will call the PPI Tech Support number tomorrow (or maybe
Monday) to see if I have done something stupid.  If they cannot solve
the problem, I will return the modem, and cancel my order with the mail
order house.  There are many existing 2400 bps modems, and if I can't
connect with them, I consider the PPI 9600SA modem unacceptably broken.
I hope the Intel modem has better performance.

After this experience, I have had a couple of problems with the 9600SA
on a 9600 bps connection.  Occasionally, I will hear a couple of relay
clicks out of the modem, and while the LEDs stay on indicating OH and
Carrier Detect, the modem connection is non-existant.  Even after
waiting 30 seconds or so to allow for retraining showed that the modems
are not connected any more, despite the front panel lights.  This has
happened probably 2 or 3 times over about 50 login attempts.

Conclusions:

The PPI 9600SA is _USELESS_ at speeds under 9600 (4800) bps.

	I consider this absolutely unacceptable.

Disallow Data Compression for higher data transfer rates,
	on ALL types of files!

Errata:

issuing the ATI3 command shows the modem is:
PM9600SA Version 1.05  (c) Practical Peripherals, Inc. 1990

My existing 2400 bps modem is an Avatex 2400.

-- 
favourite oxymorons:   student athlete, military justice, mercy killing
Ken Hendrickson N8DGN/6       kjh@usc.edu      ...!uunet!usc!pollux!kjh