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      STACKER NOTE                                         STACKER NOTE
                        WHAT IS "PRELOADING" STACKER?
                          (Applies to Stacker 4.0)
      STAC FAX  4516 (04-08-1994)
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      BACKGROUND
      
      During a computer's Startup process, certain things load into
      memory in a specific sequence. As a simplification, your computer
      firsts tests hardware, reads some hardware configuration
      information, loads the Disk Operating System (DOS) into memory,
      then reads and executes the boot files, CONFIG.SYS and
      AUTOEXEC.BAT. If the Stacker driver is loaded after DOS but
      before the CONFIG.SYS file executes, it is said to be
      "preloading".
      
      What is required to preload Stacker?
      
      You need a version of Stacker that is capable of being preloaded,
      and a version of DOS that supports preloading. Stacker versions
      3.1 and 4.0 may be preloaded. MS-DOS version 6.x, Novell DOS 7,
      and PC-DOS version 6.x with system file dates 9/30/93 or later,
      support preloading compression.
      
      How do I know if Stacker is preloading?
      
      Examine the CONFIG.SYS file. Type ED /C <enter>. Look for the
      Stacker lines in the file. If one of them is similar to the line
      below, then Stacker does NOT preload:
      
           DEVICE=C:\STACKER\STACKER.COM
      If you do not see a STACKER.COM statement, and you have access to
      your Stacker drives, then your Stacker version is preloading. A
      typical CONFIG.SYS entry for preloading Stacker includes the
      line:
      
           DEVICEHIGH=C:\STACKER\STACHIGH.SYS
      Also note that if Stacker is preloading, there will typically be
      no CONFIG.SYS on the uncompressed boot drive.
      
      When does Stacker load into memory?
      
      The preloading Stacker driver loads into memory during the
      execution of IO.SYS (or its equivalent), and before the
      CONFIG.SYS. IO.SYS calls the Stacker device driver. The actual
      Stacker device driver is contained in a hidden file in the root
      directory of the physical drive called DBLSPACE.BIN. The Stacker
      banner displays on the screen right after the "Starting xx-
      DOS..." message. Preloading Stacker does have lines in the
      CONFIG.SYS (see the STACHIGH.SYS line above) but these lines are
      primarily for memory management. Even if they are accidentally
      deleted, Stacker will still load.
      
      Non-preloading Stacker loads into memory when its STACKER.COM
      line is executed in the CONFIG.SYS.
      
      What are the advantages of preloading?
      
      The primary advantage of preloading is safety. The Stacker driver
      (contained in DBLSPACE.BIN) is a file with the System, Hidden,
      and Read-only attributes. It is difficult to accidentally delete
      or damage this file. Also, the Stacker loading process cannot be
      interrupted by accidentally deleting the CONFIG.SYS file or
      inadvertently removing the Stacker lines from it.
      
      The new generation of DOS products that support preloading also
      support the use of DPMS. This will save precious memory resources
      when loading the Stacker driver.
      
      
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      Copyright 1994 Stac Electronics
