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From: cgordon@vpnet.chi.il.us (Crash Gordon)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: [Was Perstor...] EXPANZ triples HD capacity; vendor? Technology?
Message-ID: <277ecc91-5fe.1comp.sys.ibm.pc.hardware-1@vpnet.chi.il.us>
Date: 31 Dec 90 06:55:02 GMT
References: <9012281359.aa02212@PARIS.ICS.UCI.EDU>
Lines: 63


>Author: [Ira Baxter]
>Can you tell us a) who makes the EXPANZ card,

InfoChip Systems, Inc.
2840 San Tomas Expressway
Santa Clara, CA  95051
(800) 447-0200
(408) 727-0514

>and b) roughly how they do this?

"The exceptional power of the EXPANZ! card comes from InfoChip's
revolutionary IC-105 data compression coprocessor.  This proprietary high-
speed chip incorporates noiseless/lossless technology into an adaptive, fast
converging algorithm."

My guess is that they would intercept calls to the BIOS disk functions,
compress the data on the fly, and then write the compressed data.  (Or vice-
versa for reads.)

They do warn that they are not compatible with "Compaq DOS 3.31 and similar
proprietary adaptations", so perhaps they intercept DOS disk calls, rather
than BIOS calls.

>I didn't think there was time for enough flux transitions on a track to
>triple the number of bits.  Does the driver compress files as it writes
>them?

Bingo.

>How can work when storing, say, a .ARC file?

"File Type                      Compression
 CCITT Group III Documents         4-15:1
 Database                           3-8:1
 Image files                      1.5-7:1
 CAD/CAM Files                     2-12:1
 Word Processing and
 Spreadsheet files                  2-4:1
 Executable code                    1-2:1

 These figures are to be used as guidelines, and in no way
 represent guaranteed compression ratios.  Your actual
 performance may vary depending on the type of data stored."

They don't list ARC, LZH, or ZOO files.  Since these files are already
compressed, there will probably be little effect.  There may even be a
slight expansion due to overhead.

>I think your answer should be posted.  Enquiring minds want to know.

It's posted.  My apologies for not being "V334MWV4", though.  His reply may
be different.


-----------------------------------------------------
Gordon S. Hlavenka            cgordon@vpnet.chi.il.us
Disclaimer:  I don't own an EXPANZ! card, nor have I
ever used one.  I am not associated with InfoChip in
any way.  The quotes above are copied without permis-
sion from advertising literature sent to me by Info-
Chip.