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1993-12-14
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SMARTDRIVE OVERHAUL
SMARTDRIVE is a disk cache program that works with
computers that have extended memory. A disk cache uses
a portion of memory to store information that DOS reads
from disk. DOS can read the information from the disk
cache much faster than it can read information from a
drive. However, with DOS 6.0 Microsoft had their
SMARTDRIVE program default to both read caching and write
caching. The problem with write caching is that if you
turned your computer off immediately after quitting a
program, you could potentially lose data.
With DOS 6.2 SMARTDRIVE write caching is turned off by
default. If you upgrade to DOS 6.2 from 6.0 and you had
SMARTDRIVE write cache your drives, then SMARTDRIVE
leaves write caching turned on.
You can force DOS immediately to write the cached data to
the hard drive, by typing at the system prompt:
smartdrv /c <ENTER>
With DOS 6.2 SMARTDRIVE automatically flushes a write
cached disk before returning you to the system prompt.
This means it gets the data from memory and writes it to
the hard drive before you are returned to the system
prompt. If you are using DOS at the command line, you
should always exit your program and return to the DOS
prompt before you turn your machine off.
With DOS 6.2 Microsoft has added a new /X switch to turn
off write caching for all drives.
For most people, the SMARTDRIVE line is in their
AUTOEXE.BAT file which is a text file that resides on the
root directory of the start-up disk. See pages 205 - 208
in LEARNING DOS FOR THE COMPLETE NOVICE, 2nd Edition for
examples and exact instructions on how to use EDIT and
modify your AUTEXEC.BAT file to selectively turn off
write caching. Those people with exotic ("bus-mastering"
hard disk controllers) such as SCSI, or ESDI, may need to
have SMARTDRIVE installed in the CONFIG.SYS file. The
CONFIG.SYS file also resides in the root directory of
your start-up disk and can be viewed and modified with
the DOS EDIT program. See pages 209 through 211 in
Learning DOS for the Complete Novice, 2nd Edition, for
how to view and modify your CONFIG.SYS file.
With DOS 6.2, you could add the /X switch to turn off
write caching like so:
SMARTDRV /X
You can selectively 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.
SmartDrive does not cache compressed drives (DoubleSpaced
drives); however, for increased performance, you can
cache the host drive. If you are running DoubleSpace,
you can get information on all your drives by typing:
dblspace /i <ENTER>
If you are running DoubleSpace, the above command gives
you information about all your drives. It also tells you
which drive is your host drive. Suppose you have only
one hard drive and are running DoubleSpace. Suppose you
typed the above command and found out that your
DoubleSpace host drive is called H. If that is the case,
you can configure SMARTDRIVE to read cache, but not write
cache the host drive by changing your SMARTDRIVE line in
your AUTOEXEC.BAT file to read:
SMARTDRV H
SmartDrive does not cache network drives, or RAM drives.
With DOS 6.2, SMARTDRIVE read caches CD-ROM drives. This
is a very nice feature because CD-ROM drives are often
too slow. Caching should help performance.
If you want to see which drives SMARTDRV is caching, at
the system prompt type:
smartdrv <ENTER>
TIP
If after typing SMARTDRV <ENTER> you notice that your CD-
ROM drive is not being cached, there may be a perfectly
logical reason. The line which loads the MSCDEX program
needs to be loaded BEFORE the SMARTDRV line.
To see how to modify an AUTOEXEC.BAT or CONFIG.SYS file
see LEARNING DOS FOR THE COMPLETE NOVICE, 2nd Edition.
For most people the line that loads the MSCDEX program
(for the CD-ROM) and SMARTDRV will be in the AUTOEXEC.BAT
file. The AUTOEXEC.BAT file resides in the root
directory of the start-up disk (usually drive C).
EXOTIC HARD DRIVES
If you are one of those people who have an exotic "bus
mastering" hard drive controller, you may need to have
SMARTDRIVE load in the CONFIG.SYS file. For specific
instructions on how to modify a CONFIG.SYS file look in
Learning DOS for the Complete Novice, 2nd edition. Try
using the following line in the CONFIG.SYS file:
DEVICE=C:\DOS\SMARTDRV.EXE /DOUBLE_BUFFER
The above SMARTDRIVE command needs to come before the
DEVICE command that loads EMM386. Note that when in the
CONFIG.SYS file, SMARTDRV.EXE is used. Remember, before
an AUTOEXEC.BAT or CONFIG.SYS start up file can take
effect, you must reboot your machine. After you reboot
type:
smartdrv <ENTER>
With the above DEVICE=C:\DOS\SMARTDRV.EXE /DOUBLE_BUFFER
line in your CONFIG.SYS file the SMARTDRV <ENTER> command
loads SMARTDRIVE into upper memory. After you do that
you can type the following:
smartdrv /s <ENTER>
Here, the /S stands for Status. A table appears on your
screen that looks something like:
DISK CACHING STATUS
drive read cache write cache buffering
A: yes no no
B: yes no no
C: yes yes no
S: yes no no
Look in the buffering column. If all the entries say
"no" then your hard drive does not need this Double
Buffering and you would be better off taking the
SMARTDRIVE line out of your CONFIG.SYS file and just
using a SMARTDRV line in your AUTOEXEC.BAT file. This
Double Buffering makes SMARTDRIVE operate slower. So, if
your hard drive can support SMARTDRV in the AUTOEXEC.BAT
file, you are better off.
If you want more information about the DOS 6.2 SMARTDRIVE
program type:
help smartdrv <ENTER>
Of course, you will have to be using DOS 6.2. If you
need any help on using the DOS HELP see pages 192 - 194
in LEARNING DOS FOR THE COMPLETE NOVICE, 2nd Edition.
TIP
If you are using DOS at the command line, you should
always exit your program and return to the DOS prompt
before you turn your machine off. Make sure the rest of
the family knows this, too.