Disabling Write Caching in DOS 6

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

When you are in EDIT, you can press  for more help. If you make changes, don't forget to save the file by pressing:
   
     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

=====================================================================

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

=====================================================================

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

If you want to see which drives SMARTDRV is caching, at the system prompt type:

     smartdrv

For more information on the DOS 6 SMARTDRV command, type:

      help smartdrv

This section is finished.