baxter@zola.ICS.UCI.EDU (Ira Baxter) (12/29/90)
[I tried replying to the originating poster, v334mwv4@UBVMS.BITNET, but UBVMS cryptically responds that it can't deliver to V334MWV4. So I have posted my query here in the hopes that V334MWV4 will see it again. I have recently seen many messages from "gensyms" rather than people; is this some sort of inside joke or do people really get account names like that? On purpose?] In comp.sys.ibm.pc.hardware you [v334mwv4] write: >Another card that you may want to try is the EXPANZ card. These people claim >to triple or more the size of you hard drive. This will probably be my next >purchase. Its about $150 but the developers tell that there is a problem >with running programs like Pc Tools Compress. Can you tell us a) who makes the EXPANZ card, and b) roughly how they do this? 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? How can work when storing, say, a .ARC file? I think your answer should be posted. Enquiring minds want to know. -- Ira Baxter IDB (714) 856-6693 ICS Dept/ UC Irvine, Irvine CA 92717
jon_sree@world.std.com (Jon Sreekanth) (12/31/90)
In article <9012281359.aa02212@PARIS.ICS.UCI.EDU> baxter@zola.ICS.UCI.EDU (Ira Baxter) writes:
Can you tell us a) who makes the EXPANZ card, and b) roughly
how they do this? 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? How can work when
storing, say, a .ARC file?
PC Magazine, Nov 13, page 43, covered this card in their First Looks section.
The "fact file" summary box says :
InfoChip Systems, 2840 San Thomas Expressway, Santa Clara, CA 95051
800-447-0200, 408-727-0514. List $199
Requires any non-MCA expansion slot, 512K free RAM,. 1 MB free on hard
disk, DOS 3.0 thro 3.3.
In short : An expansion board that transparently compresses files written
to virtually any DOS disk. The savings in disk space might not be worth
the restricted use of disk utilities.
My summary of the article :
It's a half size 8 bit bus expansion card, has one ASIC sorrounded by
glue chips. The hardware is fast enough that there is no visible
inefficiency due to compression/decompression. A disk must be initialized
with the software, then a 30K driver must be left installed in RAM.
Presumably, the software traps disk access calls and forces disk data
to go through the card. Does not work with DOS 3.31, 4.0, OS/2, or
network operating systems.
Compression ratios are impressive, upto 1.6:1 for executables, 2:1 for
ascii files, 10:1 for graphics (PC Mag's test numbers).
The safety margin provided by disk utilities is lost. The product
tricks DOS into thinking the files are their original size, while
actually storing them in a compressed form in a smaller number of
sectors.
The question of compressing an already compressed (ARC'ed) file is
interesting, but was not answered in the article. Hopefully it's
smart enough not to have a larger compressed file than the original.
The right place to put compression is in the hard drive itself; this
eliminates the software hackery. Computer Technology Review, Dec 90,
had a good article on page 26. Briefly, the reason it's not already
available is : disk architectures and chips are highly integrated, and
there's no place to sneak in the compression, error correction is
more problematic, and the "transparency issue". Transparency means
issues like, for example, DOS knows the uncompressed file size, but
until compression is completed, the drive does not know the
compressed file size. (The article was written by a Maxtor Corp
engineer, so presumably drive makers are looking into the issue).
Regards,
/ Jon Sreekanth
Assabet Valley Microsystems Fax and PC products
346 Lincoln St #722, Marlboro, MA 01752 508-562-0722
jon_sree@world.std.comcgordon@vpnet.chi.il.us (Crash Gordon) (12/31/90)
>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.