___________________________________________________________________________
STACKER NOTE                                                   STACKER NOTE
Title: Performance Differences Between Stacker Software and Coprocessor 
       Versions (AT/16 and MC/16).
STAC FAX Index #2502 - 2/20/92                         
___________________________________________________________________________

Background.

   Stacker's software is supplemented and enhanced by the coprocessor card.  
   The Stacker coprocessor card yields the highest compression of data, the 
   smallest device driver and the fastest I/O.


What performance increases will I see with the coprocessor?

   1. Hardware compression offers as much as 10-20% more disk space;
   
   2. Disk reads and writes are 5-15% faster.  This higher performance 
      is especially apparent on slower 8088/8086 and 80286 machines.
   
   3. The device driver memory requirements with the Stacker coprocessor card 
      are as little as 14k vs. a minimum of 26k for the software version.

What if the coprocessor stops working?

   If the coprocessor card does not respond to the Stacker device
   driver when the system starts up, Stacker will run in the 
   software mode and produce the following message: <coprocessor not
   functioning -- invoking software driver>.  This means that Stacker 
   is fully operational,  only it is running without the benefits of 
   the card. For AT/16 trouble shooting guidelines see STAC FAX index #2001, 
   "Stacker Coprocessor Card Installation Checklist". 

Is is difficult to upgrade to the coprocessor from the software version?

   Upgrading from the software to the coprocessor version does not
   require that you re-stack your drives.  However, only those files 
   written to the drive with the coprocessor benefit from the higher
   compression.  With Stacker 2.0, all the files can be recompressed 
   by the Stacker coprocessor by running Stacker's SDEFRAG disk optimizer 
   with the /R parameter.  For example, to recompress Stacker drive C: 
   
   type:  SDEFRAG /R C:   <ENTER>

___________________________________________________________________________
Copyright 1993, Stac Electronics