textfiles/computers/cache.txt

                      DISABLING WRITE CACHING

          To avoid potential write caching problems, you may want to
          disable the DOS 6 SmartDrive write caching feature. 
          However, first you will need to know about the DOS 6
          AUTOEXEC.BAT file.
          
          Below is a typical DOS 6 AUTOEXEC.BAT file for an 80286, an
          80386, or an 80486 machine. 
          
          @ECHO OFF
          PATH C:\DOS;C:\WINDOWS;C:\UTILS
          PROMPT $P$G
          SET TEMP=C:\DOS
          SMARTDRV
          
          You can use EDIT, the built-in DOS editor, to make or modify the
          AUTOEXEC.BAT file or the CONFIG.SYS file.  Both of these
          files reside on the root directory of your start-up disk.  Remember,
          the changes you make when you modify an existing
          AUTOEXEC.BAT or CONFIG.SYS file will not take effect until
          you restart your computer.  Never make a modification to either
          the AUTOEXEC.BAT file or the CONFIG.SYS file without first
          making a backup of these important files on diskette.  If your
          start-up disk is drive C, you can load the AUTOEXEC.BAT file into
          EDIT by typing:
          
                         edit c:\autoexec.bat <ENTER>
          
          When you are in EDIT, you can press <F1> for more help.  If
          you make changes, don't forget to save the file by pressing:

                         <ALT>
                         f
                         s

          Note that the last line in the sample AUTOEXEC.BAT file is
          SMARTDRV.  SMARTDRV is a disk cache that works with
          computers that have extended memory.  If you have an 80286 or
          greater machine with at least 1 megabyte of memory, then you can
          probably use SMARTDRV.  A disk cache uses a portion of memory
          to store information that DOS reads from disk.  DOS can read
          information from the disk cache much faster than it can read
          information from a drive.  The result is that you will get a big
          performance boost if you use a disk cache.
          
          The DOS 6 SMARTDRV will cache both floppy and hard drives
          and is faster than the DOS 5 SMARTDRV.  The DOS 6
          SMARTDRV is very similar to the one that is included with
          WINDOWS 3.1 and can be loaded in the AUTOEXEC.BAT file. 
          The DOS 6 version of SMARTDRV will automatically calculate
          values by determining how much upper memory exists in your
          machine.  It will also automatically load itself into high
          memory if it is available.
          
          The DOS 6 SMARTDRV will do read caching and write caching
          for hard drives and read caching for floppies.  With write
          caching, you could lose data if you turn your computer off
          immediately after quitting a program.

          IT IS BEST TO WAIT AT LEAST FIVE SECONDS AFTER YOU QUIT AN
          APPLICATION BEFORE YOU TURN THE MACHINE OFF.

          On drives that are write cached, SMARTDRV waits until the
          cache is about full, or until there has been about 5 seconds of
          idle time, before writing the data to your hard drive.  If you
          want to force the write cache to immediately write the data to
          the hard drive, type:
          
                         smartdrv /c <ENTER>

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          To avoid potential write caching problems, you may want to
          disable the DOS 6 SmartDrive write caching feature.

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          You can disable write caching by following the SMARTDRV
          command with the letters of your hard drives.  Suppose you had
          hard drives C, D, E, and you wanted to disable write caching on
          these drives.  Use the DOS EDIT program to change the
          SMARTDRV line in the AUTOEXEC.BAT file to read the
          following:
          
          SMARTDRV C D E 
          
          The above line tells DOS to allow read caching while disabling
          write caching for drives C, D, and E.  Don't try to cache a
          DoubleSpaced drive.  SmartDrive will not cache compressed
          drives (DoubleSpaced drives), CD-ROM drives, network drives,
          or RAM drives.  If you are running DoubleSpace, you can get
          information on all your drives by typing:
          
                         dblspace /info <ENTER>
                    
          If you want to see which drives SMARTDRV is caching, at the
          system prompt type:
          
                         smartdrv <ENTER>
          
          For more information on the DOS 6 SMARTDRV command, type:
          
                          help smartdrv <ENTER>




     This section is finished.  It is an excerpt from LEARNING DOS FOR
     THE COMPLETE NOVICE, by Steven Woas, copyright 1993.  When you register
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