GEMini Atari/GEMini_Atari_CD-ROM_Walnut_Creek_December_1993.iso/files/diskutil/fatcache/fatcache.doc

Text File | 1993-01-26 | 11KB | 233 lines

FATCACHE v1.0 Documentation "FATCACHE.DOC"
==========================================

Fatcache Written By Phil Jensen (CIS:70004,1416)
           added to by Tim Rule (CIS:100135,2013)
Install utility and documentation by Tim Rule

This material is Public Domain.  You may distribute and make as
many copies of this program as you like.  In fact the system
relies on you giving copies to friends, BBSs, and Public Domain
libraries.  The authors remain copyright holders of all material
supplied with this software.

YOU USE THIS PROGRAM ENTIRELY AT YOUR OWN RISK AND THE AUTHORS
ARE NOT RESPONSIBLE FOR ANY LOSS OF DATA OR FOR ANY OTHER
LIABILITIES THAT MAY RESULT FROM THE USE OF THIS UTILITY.

Overview:

Fatcache is a hard disk cache.  This means that it will speed up
some hard disk operations.  The utility also incorporates a
section to speed up the slow hard disk operation of versions 1.0
and 1.2 of TOS.  The net result of both the cache and "FAT"
acceleration is a huge increase in speed of some disk operations.

When copying a batch of files between partitions of a hard disk
the speed increase over the normal routines may often be in
excess of 1000%.  That means that an operation which would
previously have taken an hour would only take six minutes with
fatcache installed.

The cache should work with all versions of the operating systems
but the FAT acceleration is only beneficial for versions 1.0 and
1.2 of TOS.  Versions from 1.4 onwards have their own improved
disk performance built in.  When the program runs on bootup it
will detect the date of the ROM in your machine and if the date
is not recognised as either a TOS 1.0 or TOS 1.2 ROM then a
message will be displayed and FAT acceleration will be disabled.

Fatcache assumes drive C is your boot drive and contains the auto
folder.

WARNING:  Fatcache 1.0 is only for NON-REMOVABLE DRIVES.  If you
have a removable drive in the range C-L then you must disable
fatcache on that drive.  This covers such drives as removable
hard disks (e.g. Sequest R44), floptical drives, MO drives, CD-
ROMS etc.

NOTE:  This utility has been used on our own machines for a long
time without any problems.  However, as with any utility which
works closely with your hard disk, there is always a risk of data
loss if other programs interfere with fatcache.  If files appear
to be becoming corrupted, or directorys become scrambled, you
should make sure that the hard disk is not being accessed and
switch of the computer immediately, before writing to the hard
disk again.  There is most likely a conflict between programs in
your auto folder and you should avoid having the same programs
installed at once.  One possible solution is to put FATCACHE.PRG
before some other auto folder programs.  This can be done from
the desktop by copying all the files in the auto folder into
another folder, deleting all files in the auto folder, and
copying the files back into the auto folder in the order you
desire.

Using Fatcache:

Operation of fatcache has been made as simple as possible.  The
program FATCINST.PRG is the installation/configuration program
for fatcache.  You will probably want to copy this file onto your
hard disk.  To install fatcache you should run FATCINST.PRG from
the desktop.  This program will display a dialog box presenting
the various options of fatcache.  To install fatcache on your
hard disk or boot floppy you should select "Yes" for auto
installation.  The FAT acceleration option should normally be
"ON" telling fatcache to enable FAT acceleration if possible.  If
your version of the operating system is not supported then
fatcache will not use FAT acceleration anyway.  The "OFF" option
disables FAT acceleration and is useful if you have TOS 1.0/1.2
but don't want this facility.  Switching off FAT acceleration on
a machine with TOS 1.4 or later will stop the message displaying
that FAT acceleration has not been installed.

On the right-hand side of the dialog box are the drive
enable/disable switches.  Normally all of these switches will be
enabled and fatcache will automatically detect which ones are
hard disks.  However, if you wish to disable cacheing and FAT
acceleration on one of your drives, or if fatcache has
incorrectly determined that a drive is a hard drive when in fact
it is another type (CD-ROM or RAM-DISK), then you do so by de-
selecting the relevant drive letter.  You should disable cacheing
on a RAM disk if it is in the range C-L as cacheing them is
unecessary. (I would suggest changing your RAM disk to drive M).

The buffers field at the bottom of the dialog specifies how many
buffers the program should use for cacheing.  The more buffers
used the more effective the cache is likely to be.  However, if a
large number of buffers are specified then you may notice that
disk access slows down.  I have found a number between 48 and 128
effective, although 255 is the maximum number.  Another
consideration is, the more buffers, the more memory is used up.
The cache uses approximately 1K for every 2 buffers.  48 buffers
is sufficient for effective use of the FAT acceleration and is
very economic with memory.

The "install immediately" box on the form will cause fatcache to
be installed into memory immediately if it has not already been
installed.  This prevents the need to re-boot if fatcache has not
already been installed, but may not always be reliable. Automatic
installation after the next re-boot is recommended.

When you have selected all the options you want you should click
on "Save" to save that configuration or "Cancel" to cancel your
options and return to the desktop.

If you said "Yes" to automatic install then the install program
will create the program, FATCACHE.PRG in the AUTO folder of drive
C.  Fatcache will be installed into memory next time you boot
from drive C.

Any changes you made to the configuration will come into effect
next time fatcache is installed, usually the next time you boot-
up.

Files:

FATCACHE.LZH is a compressed file containing this document and
the rest of the fatcache files.  You may have X_FATCHE.TOS
instead which is a self extracting version of FATCACHE.LZH.  It
is quite likely that fatcache was not supplied to you compressed
in which case you will not have either of these files and will
not have had to uncompress fatcache.

FATCINST.PRG is the installation and configuration program for
fatcache.  To use fatcache you only need to run this program and
select options (see Using Fatcache above).  FATCINST.PRG actually
contains the program FATCACHE.PRG (see below).  If you specify
automatic installation then FATCINST.PRG will create FATCACHE.PRG
for you.

FATCINST.RSC is the GEM resource file for the installation
program.  You must have this file in the same folder on your hard
disk as FATCINST.PRG in order to run FATCINST.PRG.  If you copy
FATCINST then you must copy both FATCINST.PRG and FATCINST.RSC.


FATCACHE.PRG is the actual fatcache program which loads the disk
cache/accelerator into memory.  It is best run form the auto
folder.  This program is all that is needed to use fatcache
although without FATCINST.PRG you will not be able to change the
configuration of the program.  Do not copy this file if you wish
to give fatcache to someone else or upload to a bulletin board.
A copy of it is kept inside FATCINST.PRG for when fatcache is
installed on another hard disk.

Giving away fatcache:

You are encouraged to give fatcache away to as many people as you
can.  When you give it away you can give either just the file
called X_FATCHE.TOS on its own or the file FATCACHE.LZH (if you
have either).  Altenatively the three files, FATCINST.PRG,
FATCINST.RSC and FATCACHE.DOC.  Do not give away FATCACHE.PRG as
this is your personal version for your settings.  If you send a
disk with fatcache on it to a Public Domain library which does
not already have fatcache then, in return, they will usually give
you a disk of your choice from their catalogue.

THE FOLLOWING SECTIONS ARE FOR PROGRAMMERS AND DO NOT NEED TO BE
READ IN ORDER TO USE FATCACHE.

Technical Notes:

Fatcache installs itself into the hdv_drv vector ($476.L) which
is called when the bios rwabs function is called.  Read and write
operations are thus intercepted by fatcache and either acted upon
or passed on the the bios rwabs routine.  The program will in
fact only operate on single sector reads, multiple reads are
currently allowed to fall through.  This is not a problem as TOS
1.0 and all other versions up to current read FATs and other
useful system data using single sector reads.  It is the cacheing
of these sectors which is most beneficial and cacheing multiple
reads introduces other problems (e.g. loading a large program
would clear out all the useful sectors in the cache).  The cache
defaults to write-through meaning that there is no risk of the
data stored on a non-removable disk becoming out-dated.

Fatcache will only work with 512 byte sectors.  If non-standard
sectors are detected then the program will refuse to install.

The FAT speed-up, if enabled, will take over from the GEMDOS
during two operations, counting free sectors, and searching for
free sectors.  Unlike other fat speed-up programs fatcache does
not actually replace or change any GEMDOS code, rather it does
the job of the GEMDOS code, very quickly, and then fools that
routine into thinking it has finished its job.  This is quick,
simple and effective.  Also it is very memory efficient.  The FAT
speed-up routines are ROM dependent and so the installation code
within FATCACHE.PRG modifies the speed-up code according to the
ROM date.  ROMs supported in this release are as follows:
       11/20/85 - Tos 1.0
       04/24/86 - Tos 1.2
     any other date will result in the FAT speed-up being
disabled.  The FAT speed-up routines are designed only for hard-
disks, therefore only 16-bit FAT entries are supported.

Source code for FATCACHE.PRG is available from Tim Rule through
CompuServe. (100135,2013).  Source may also be found in the
ATARIPRO libraries.  This program has been released into the
public domain because we thought that it would be useful to other
people.  We make no promises to continue support for this program
in the future but if you find any bugs or have suggestions you
can contact us on CompuServe or by mail.

ADDRESSES (as of 9 January 1993)

Tim Rule
26 Redding Drive,
Amersham,
Buckinghamshire.
HP6 5PX
United Kingdom

   or

Philip H. Jensen
172 Durnell Ave.
Boston, MA 02131
USA