textfiles/computers/cache.txt

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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
this program, you will receive the 336 page book, LEARNING DOS FOR THE
COMPLETE NOVICE which covers DOS 3.2 through DOS 6. To register send
$15.95 plus $2.00 for shipping to:
Celestial Press
4424 Dohrcrest Dr.
Suite C
New Port Richey, FL 34652
Phone (813) 845-8522
US customers can order toll-free 1-800-330-3311
Fax (813) 845-8522
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