[comp.sys.ibm.pc.misc] DoubleDisk

umhudso7@ccu.umanitoba.ca (Wayne Hudson) (10/26/90)

  I've heard some OUTRAGEOUS stories about a HD compression program
out there called DoubleDisk.  Supposedly it does stuff like 'writing
between the tracks' and ultrafast de/compression.  I've heard some
hard to believe claims of 120meg from an actual 20(twenty)meg drive!
Maybe I should be posting this to sci.skeptics as well...
What's anyone out there know about DoubleDisk?
-- 
Wayne Hudson                "Optimism:the belief that everything will work out
- umhudso7@ccu.umanitoba.ca  fine. Irrational, bordering on insane" K9, Dr. Who

david@gisatl.FIDONET.ORG (David Deitch) (10/30/90)

You won't believe this, but back on 26/Oct/90 (was a Fri BTW) at
about 16:54, this Wayne Hudson said this to All:

 >   I've heard some OUTRAGEOUS stories about a HD compression program
 > out there called DoubleDisk.  Supposedly it does stuff like 'writing
 > between the tracks' and ultrafast de/compression.  I've heard some
 > hard to believe claims of 120meg from an actual 20(twenty)meg drive!
 > Maybe I should be posting this to sci.skeptics as well...
 > What's anyone out there know about DoubleDisk?

     Double Disk is rather simple in concept although I won't pretend 
to understand its innerds.  It takes over a large file, say 10 meg in 
size.  It then fills the file with a compressed logical drive format 
based on the virtual size you specify.  The driver then compresses 
and decompresses clusters written to and read from the logical drive 
name assigned to the file.  The actual capacity of the drive is based 
on the ability of the data to be compressed.  It is a good program 
for its price.  It can be defragged (although they recommend against 
it), can be sector edited (although they recommend against it), and 
is not too slow on a 386, although there is some slag time due to 
compression algorithms.  

     It is a large device driver, 50K that can not be loaded hi 
because there is a com program that activates it that won't find it 
hi.  As to the size, 120M is virtual capacity only and that has to do 
with the compression level used and the format of the drive.  
Realistic compression ratios run about twice the physical capacity 
(ergo the name).  Both this program and the Expanz! kit from InfoChip 
provide adquate expansion at varying degrees of loss.

     David Deitch (GIS)
          deitch@gisatl.fidonet.org
               1:133/411@fidonet
 

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