ACACHE

Acer Disk  Cache (ACACHE) is a utility program that improves
fixed disk  drive performance.   Acer Disk Cache reduces the
number of  disk reads  and  writes,  improving  the  overall
response time for most applications.

The disk  cache utility creates a cache buffer in memory and
stores frequently  accessed disk  data there.   Whenever the
processor requests  a disk  read, disk cache first looks for
the data  in the  cache buffer.  If the data is in the cache
buffer, it is loaded from the buffer instead of the disk.
Acer Disk Cache has several configurable features:

.    Write caching     Disk-write data  can be automatically
copied to cache buffer memory.

.    Smart write     When a  disk write  is requested,  disk
cache first  checks to  see if the data has changed since it
was last read.  If it hasn't changed, no write takes place.

.  Cache buffer location  The cache buffer can be located
in base, extended, or expanded (using EMS) memory.

.  Cache buffer size  Cache buffer size in kilobytes (KB)
is adjustable.

.  Page size  The number of sectors per page  is
adjustable.

.  Boot startup  Acer Disk Cache is loaded when the
system boots.  It can be configured to activate immediately
after boot or after a DOS command.

In most cases, the default configuration is the most
efficient for typical PC applications.  However, the program
permits configuration.  A larger cache buffer, in general,
gives better cache performance.

Acer Disk Cache includes a DOS command line interface,
making it easy to control the disk cache functions from the
DOS prompt:

.  Setup  Allows easy  custom configuration of disk cache
parameters from a menu.

.  Help  Provides on-line descriptions of the disk cache
program and quick reference instructions for running it.

.  Flush  Clears the disk cache buffer and statistics
information.

.  Shutdown  Enables or disables disk caching.

.  Status Reports  Displays the disk cache driver status
and run statistics.

.  Feature Control  Enables or disables cached disk
writes and smart write mode.

What You Need To Run Acer Disk Cache

To run Acer Disk Cache a machine requires:

.  MS-DOS version 3.0 or higher

.  Fixed disk drive (disk caching doesn't run with
diskette drives)

.  At least 256 KB of base memory, if the cache buffer is
located in base memory

Installing Acer Disk Cache

The Acer Disk Cache utility contains two files --
ACACHE.EXE, an executable file that allows you to customize
cache parameters and ACACHE.SYS, the device driver.

Begin the installation by running ACACHE.EXE in Setup mode.

1.  Insert the Acer Disk Cache distribution disk into drive
A and type:

A:ACACHE/SETUP

2.  Press Enter.  The setup screen appears:


                  Setup  Program
        Acer Disk Cache Driver Version
      X.XX

         Boot drive :       C
         Buffer in  :    Extended Memory
         Buffer size:     256 KB
         Page length:       8 Sectors

         Turn On/Off:      On
         Cache write:      On
         Smart write:      On

          1. Press  ,  to move cursor
          2. Press SPACE to select values
          3. Press F10   to save new setup
          4. Press ESC   to EXIT

The setup  screen displays  seven  default  parameters.
These parameter values are correct for most systems.

3.  To change parameters, use arrow keys to move the
highlight to the parameters you want to change.

4.  Press the space bar to display the desired value.

5.  To change the buffer size, press the backspace key to
remove the old value.  Enter the correct value.

6.  Press F10 and type Y to save the new setup parameters
and copy the disk cache files to your fixed drive.

Setup also modifies the CONFIG.SYS file on your fixed drive
to start the ACACHE.SYS device driver automatically  each
time the system boots.  The following screen appears:


      Creating backup file ==> C:\CONFIG.BAK
      Updating ==> CONFIG.SYS
      Copying ACACHE.SYS ==> C:\ACACHE.SYS
      Copying ACACHE.EXE ==> C:\ACACHE.EXE

      Cache driver setup successful
      Reboot to install the disk cache


7.  Remove the diskette from drive A and press the reset
button to reset the system.  Acer Disk Cache automatically
starts running.  When the disk cache driver is installed
(after boot), the system displays the condition of the
program.  If you used the default parameter values (in
Setup) the display looks like this:


      Acer Disk Cache Driver  Version X.XX

      Cache buffer in   :    Extended memory
      (200000h)
      Cache buffer size :     256 KB
      Cache page length :       8 Sectors

      Turn On / Turn Off:      On
      Cache write       :      On
      Smart write       :      On

      Acer Disk Cache successfully installed


Using Acer Disk Cache

This section  describes the syntaxes for invoking ACACHE.EXE
and ACACHE.SYS on the distribution disk.

ACACHE.SYS is an installable device driver that manages a
portion of the computer memory as a disk cache.  ACACHE.EXE
controls the device driver and displays cache status and
statistics.  ACACHE.EXE also provides a help command  and
installs the disk cache onto a fixed disk drive.

ACACHE.SYS -- Disk Cache Device Driver

ACACHE.SYS is invoked in CONFIG.SYS.  The command line
included in CONFIG.SYS has the following syntax:

     DEVICE = ACACHE.SYS [sssss] [/Pxx] [ /B | /A | /E | /LOADALL]
                         [/OFF] [/CW] [/SW]

sssss

Cache buffer size in KB.  The valid  range is  from 64 to
15360 (64  KB to  15 MB).  Default value is 128 KB for base
memory and 256 KB for expanded or extended memory.

/Pxx

Cache page size in sectors.  Valid values for xx are 1, 2,
4, 8, and 16.  The default value is 4 sectors.

/B,
/E,
/A,
/LOADALL

Specifies which memory the cache buffer is located in.  

/B locates the cache buffer in base memory (below 640 KB).

/E locates the cache buffer in extended memory (above 1 M).
Data is moved in and out of extended memory using the BIOS
block move call (INT15 BLKMOV).

/A locates the buffer in expanded memory.  The EMM driver
must be installed before installing the disk cache.
/LOADALL should be used on 80386 machines instead of /E for
better performance.  /LOADALL uses the 80386 LOADALL
instruction to transfer data to and from extended memory.

/OFF

Disables disk caching.  If no switch is included in the
command line, system boots with disk caching enabled.

/CW

Enables caching disk write data.  If no switch is included
in the command line, disk write data is not cached.

/SW

Enables smart write mode.  If no switch is included in the
command line, smart write mode is disabled.



ACACHE.EXE -- Disk Cache User Interface

ACACHE.EXE is a DOS command that configures disk cache
options, installs the disk cache onto a system, and provides
status and statistic reports.  The syntax of ACACHE.EXE is:

     > ACACHE [ /SETUP | /HELP | /STATUS | /FLUSH | /ON |
                /OFF   | /NOSW | /SW     | /NOCW  | /CW ]

/SETUP

Runs the menu driven setup program for configuring disk
cache parameters.

/HELP

Displays the help screens.  May be abbreviated /H.

/STATUS

Displays the cache driver status and statistics.  May be
abbreviated /ST.

/FLUSH

Flushes the cache buffer and statistics information.

/ON

Turns on disk caching.  If the cache buffer is located in
expanded memory, ACACHE.SYS will request EMM to allocate
expanded memory.

/OFF
Turns off disk caching.  If the cache buffer is located in
expanded memory, EMM deallocates the cache buffer memory and
makes it available to other applications.

/NOSW

Disables smart write mode.

/SW

Enables smart write mode.

/NOCW

Disables cached disk writes.

/CW

Enables cached disk writes.

The Setup screen displays seven parameters to be set up for
disk cache.  The default  values (as  shown) are correct for
most systems.

                  Setup  Program
        Acer Disk Cache Driver Version X.XX

         Boot drive :       C
         Buffer in  :    Extended Memory
         Buffer size:     256 KB
         Page length:       8 Sectors

         Turn On/Off:      On
         Cache write:      On
         Smart write:      On

          1. Press  ,  to move cursor
          2. Press SPACE to select values
          3. Press F10   to save new setup
          4. Press ESC   to EXIT

To change parameters, use the arrow keys to highlight the
parameters you want to change.  Press the space bar until
the correct value for the parameter is displayed.  To change
the buffer size, press the backspace key to remove the old
value.  Then, key in the correct value.

There are four help screens.  The PgUp and PgDn keys move
the display  from one  screen to  the other.   Press  Esc to
exit.

The status and statistics displays the  current disk cache
parameters as configured in the setup screen.  If ACACHE.EXE
changes any parameters, the status display shows the new
values.

The statistics indicate how much the disk cache is saving.

The total reads from the cache divided by the total read
requests is the hit ratio.  The higher the hit ratio, the
more disk reads the disk cache is saving.

If smart writes are enabled, the smart write line and smart
write ratio indicate how many disk writes are saved by using
the disk cache.


                Status & Statistics
        Acer Disk Cache Driver Version X.XX
        Cache buffer in      :
        Extended memory
        Cache buffer size    :     256 KB
        Cache page length    :       4  sectors

        Cache status         :      On
        Cache write          :      On
        Smart Write          :      On

        Total read requests  =    2562  sectors
        Reads from cache     =    1404  sectors
        Read hit ratio       =   54.80 %

        Total write requests =     282  sectors
        Smart writes saved   =       3  sectors
        Smart write ratio    =    1.06 %

        Average read size    =    1.73  sectors
        Average write size   =    1.00  sectors

Flushing the cache buffer and statistics is useful when you
want to see how much you gain on a particular software
program by  using the  disk cache.  Type the ACACHE /FLUSH
command before starting your program.

> ACACHE /FLUSH

Disk cache buffer flushed

After your application finishes, use the ACACHE /STATUS
command to see what the read hit and write hit ratios were.
Some programs require large  amounts of data from several
locations on the disk.  These programs do not run well with
disk caching.  Turn off disk caching by typing:

> ACACHE /OFF

Disk caching disabled

You can, of course, use the ACACHE /STATUS command to see if
it is  necessary to  turn off  disk caching for a particular
program.

Restart disk caching by typing:

> ACACHE /ON

Disk caching enabled

The /SW switch improves the performance of applications that
frequently write the same data to disk.  Certain data base
management systems see improved performance under smart
write.

Smart write reduces the number of disk writes made on your
system.  Whenever data in the cache buffer is written to
disk, disk cache first checks if the data has been changed
since the last time it was written.  If there have been no
changes, nothing is written to the disk.

The /CW switch improves the performance of applications that
repeatedly read and write the same data (such as disk sort
utilities and data base management systems).

The /CW switch enables caching disk write data.
Whenever data is written to the disk, it is also copied
to cache memory.  Caching write data can sometimes
result in an extra disk read.  If the write  data is
smaller than the page size of the cache buffer, the disk
cache reads additional data from the disk to fill up the
memory page if that page is not already in the cache
buffer.  For example, if the page size is four sectors,
a data write of two sectors will be followed by an
additional read of two adjacent sectors to fill up the
memory page as long as that page is not already in the
cache buffer.

ACACHE.EXE Messages

** No operand
   Type ACACHE/HELP for help

Type ACACHE/HELP for a list of operands.

** Too many operands
   Command ignored

Only one operand is allowed per ACACHE command line.  Re-
enter the command with one operand.

** File ===> ACACHE.SYS not found

An attempt was made to install disk cache from the fixed
disk.  Log on to drive A before installation.

** Acer Disk Cache driver not installed
   Command ignored

The disk cache driver is not installed on your machine.
Check CONFIG.SYS to see if the ACACHE.SYS device driver was
installed.

** Disk cache buffer flushed

This indicates that the ACACHE/FLUSH command has executed
successfully.  The disk cache buffer has been cleared and
cache statistics are reset.

** Can't deallocate EMM pages
   Disk cache driver can't be disabled

This indicates an error in EMM when attempting to deallocate
cache buffer memory.  Check the EMM software device driver
installation and the EMM hardware.

** EMM buffers deallocated (xxxx pages)
   Disk caching disabled

When running the disk cache from expanded memory, the EMM
deallocates the cache buffer memory after disk caching is
disabled.  No action is required.

** Disk cache driver already enabled
   Command ignored

Disk caching is already enabled.

** Smart write disabled

This indicates ACACHE /NOSW command has executed
successfully.

** Smart write enabled

The ACACHE /SW command executed successfully.

** Cached disk writes enabled

The ACACHE /CW command executed successfully.

** Cached disk writes disabled

The ACACHE /NOCW command executed successfully.

** Unknown operand
   Command ignored

Type ACACHE /HELP for a list of commands and operands.  Note
the correct syntax and re-enter the command with the correct
operand.

ACACHE.SYS Messages

** ACACHE found an internal fatal error

An internal  fatal fault  was found.   The  disk cache  shut
itself down.   Check the system hardware or the EMM hardware
(if your system uses EMM).

** Too many bad sectors found

This means  there are  more than 100 bad pages on your fixed
disk.   The disk  cache shut itself down.  Disk cache cannot
run on this particular disk drive.

** Acer Disk Cache is already installed

This appears when you attempt to install the disk cache more
than  once.  The second attempt is ignored.

** Cache size adjusted to xxxxx KB

The cache buffer size has been changed to xxxxx KB.

** DOS (base) memory insufficient

There is   not enough base memory on your system to run Acer
Disk Cache.

** Invalid machine model (286 or 386 expected)

The /LOADALL  and /E  operands are only allowed on 80286 and
80386 systems.

** Available space less 64K (reserve 64K for DOS)

There is  not enough  memory on your system to run Acer Disk
Cache.

** Invalid cache size or environment

The specified  cache  size  was  illegal  or  some  expected
component was not found.

** Invalid cache size operand

The cache size must be specified in KB and be between 64 and
15360.

** Invalid page size

The utility  allows only  page sizes  of 1,  2, 4,  8, or 16
sectors.  Re-enter the command with a valid page size.

** Invalid command line operands

An unknown command switch was included in the command line.

** Duplicate or mutually exclusive operand

A switch  was included  on the  command line  twice  or  two
inconsistent operands were included on the command line (for
example, /A and /E).

** Acer Disk Cache successfully installed

The disk cache installable device driver is installed.

** Acer Disk Cache installation failed

DOS could  not install the installable device driver.  Check
the device  command syntax  in CONFIG.SYS.   Also  check for
conflicts between  device  command  switches  and  available
resources on your system.

** Can't find hard disk

Disk cache only works on systems with a fixed disk.

** DOS version 3.0 or above is required

This indicates an invalid DOS version.

** EMM version 3.2 or above is required

The EMM version is invalid.

** Can't find EMM driver

You must install the EMM driver before  entering ACACHE /A.

** Can't access EMM driver

Access to  the EMM device driver failed.  Check EMM software
driver  installation and EMM hardware.



** General EMM function call error

EMM  function  call  failed.    Check  EMM  software  driver
installation and EMM hardware.

** EMM page allocation fault

Attempt  to  allocate  cache  buffer  memory  (through  EMM)
failed.   Check EMM  software driver  installation  and  EMM
hardware.
