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15 Preventive maintenance (Introductory Macintosh FAQ)


This article is from the Introductory Macintosh FAQ, by Elliotte Rusty Harold elharo@shock.njit.edu with numerous contributions by others.

15 Preventive maintenance (Introductory Macintosh FAQ)

You wouldn't drive your car 100,000 miles without giving it a
tune-up. A computer is no different. Regular tune-ups avoid a lot
of problems. Although there are Mac mechanics who will be happy to
charge you $75 or more for the equivalent of an oil change, there's
no reason you can't change it yourself. The following ten-step
program should be performed about every three months or when you're
experiencing problems.


Many of the operations that follow will run faster and more
smoothly the more free disk space there is to work with, so spend
a little time cleaning up your hard disk. If you're at all like
me, you'll find several megabytes worth of preferences files for
applications you no longer have, archives of software you've
dearchived, shareware you tried out and didn't like, announcements
for events that have come and gone and many other files you no
longer need. If you're running System 7 you may also have several
more megabytes in your trash can alone. Throw them away and empty
the trash.


Some Macintoshes attract extensions like a new suit attracts rain.
Seriously consider whether you actually need every extension and
control panel in your collection. If you don't use the
functionality of an extension at least every fifth time you boot
up, you're probably better off not storing it in your System
Folder where it only takes up memory, destabilizes your system,
and slows down every startup. For instance if you only read PC
disks once a month, there's no need to keep Macintosh PC Exchange
loaded all the time. Cutting back on your extensions can really
help avoid crashes.


The Desktop file/database holds all the information necessary
to associate each file with the application that created it.
It lets the system know what application should be launched when
you open a given file and what icons it should display where.
Depending on its size each application has one or more
representatives in the desktop file. As applications and files
move on and off your hard disk, the Desktop file can be become
bloated and corrupt. Think of it as a Congress for your Mac.
Every so often it's necessary to throw the bums out and start
with a clean slate. Fortunately it's easier to rebuild the
desktop than to defeat an incumbent.

One warning: rebuilding the desktop will erase all comments
you've stored in the Get Info boxes. Under System 7 Maurice
Volaski's freeware extension CommentKeeper will retain those comments
across a rebuild. See


CommentKeeper also works with System 6 but only if Apple's
Desktop Manager extension is also installed.

To rebuild the desktop restart your Mac and, as your
extensions finish loading, depress the Command and Option keys.
You'll be presented with a dialog box asking if you want to rebuild
the desktop and warning you that "This could take a few minutes."
Click OK. It will take more than a few minutes. The more files you
have the longer it will take. If you're running System 6 you may
want to turn off MultiFinder before trying to rebuild the desktop.

If you're experiencing definite problems and not just doing
preventive maintenance, you may want to use Micromat's freeware
utility TechTool. TechTool completely deletes the Desktop file
before rebuilding it, thus eliminating possibly corrupt data
structures. Furthermore it doesn't require you to remember any
confusing keystroke combinations. See



All Macs from the original 128K Thin Mac to the PowerMac 9500
contain a small amount of battery powered RAM that holds certain
settings that belong to the CPU rather than the startup disk, for
example the disk to start up from. Unfortunately this "parameter
RAM" can become corrupted and cause unexplained crashes. To reset
it under System 7 hold down the Command, Option, P, and R keys
while restarting your Mac. Under System 6 hold down the Command,
Option, and Shift keys while selecting the Control Panel from the
Apple menu, and click "Yes" when asked if you want to zap the
parameter RAM. Alternatively you can use MicroMat's free utility
TechTool which doesn't require you stretch your fingers across the
keyboard like a circus contortionist. See


Zapping the PRAM erases the settings of most Apple Control
Panels including the General Controls, Keyboard, Startup Disk,
Mouse, and Map. It also erases the Powerbook 100's non-volatile
RAM disk. Thus after zapping the PRAM you will need to reset these
Control Panels to fit your preferences. One setting that zapping
the PRAM does not erase is the date and time; but since the internal
clock in the Macintosh is notoriously inaccurate you'll probably want
to reset it now anyway.

RESIZE THE SYSTEM HEAP (System 6 Only) (4.5)

Even after rethinking their extensions as per step two, most
people still have at least half a row of icons march across
the bottom of their screen every time they restart. All these
extensions (and most applications too) need space in a section of
memory called the System Heap. If the System Heap isn't big enough
to comfortably accommodate all the programs that want a piece of
it, they start playing King of the Mountain on the system heap,
knocking each other off to get bigger pieces for themselves and
trying to climb back on after they get knocked off. All this
fighting amongst the programs severely degrades system performance
and almost inevitably crashes the Mac.

Under System 7 your Macintosh automatically resizes the
system heap as necessary, but under System 6 you yourself need
to set the system heap size large enough to have room for all your
extensions and applications. By default this size is set to 128K,
way too small for Macs with even a few extensions. The system heap
size is stored in the normally non-editable boot blocks of every
system disk. Bill Steinberg's freeware utility BootMan not only
resizes your system heap but also checks how much memory your heap
is using and tells you how much more needs to be allocated. If
you're running System 6, get BootMan, use it, and be amazed at
how infrequently your Macintosh crashes. See



System files can become corrupt and fragmented, especially
if you've stored lots of fonts and desk accessories inside them.
Merely updating the System software will often not fix system file
corruption. I recommend doing a clean reinstall. Here's how:

1. Move the Finder from the System Folder onto your desktop.

2. Rename the System Folder "Old System Folder."

3. If you're installing System 6, 7.0, 7.0.1 or 7.1 shut down
and then boot from the Installer floppy of your system disks.
If you're installing System 7.5, quit all running applications
and launch the installer on the first installer disk.

4. Double-click the installer script on your System disk. Then
choose Customize... Select the appropriate software for your
model Mac and printer. You could do an Easy Install instead,
but that will only add a lot of extensions and code you don't
need that waste your memory and disk space.

If you're installing System 7.5 type "Command-Shift-K" which is
the magic code to get the installer to do a clean install.. A
dialog will pop up. Select the radio button that says "Install
New System Folder" and click OK.

From this point on just follow the installer's instructions.
Mostly you'll just need to swap disks. After installation is
finished the installer will ask you to restart your Mac. You
don't really have any choice so go ahead and restart.

5. If you installed System 7.0 or 7.0.1, you should now install
System 7 Tuneup 1.1.1, available from


If you installed System 7.1, 7.1 Pro or 7.1.2, then you should
also install System Update 3.0, available from


If you installed System 7.5, 7.5.1 or 7.5.2 then you should also install
System 7.5 Update 2.0, available from


This will bring you to System 7.5.3. Finally you should install the
System 7.5.3 Revision 2 update, available from


6. Copy any non-standard fonts and desk accessories out
of the old System file into a temporary suitcase.

7. Trash the Finder file on desktop. Now go into the Old System
Folder and trash the System, MultiFinder, DA Handler, and all
other standard Apple extensions and control panels. These were
all replaced in the new installation. If you were running
System 7.x, move everything left in the Extensions, Control Panels,
Apple Menu Items and Preferences folders into the top level of
the new System Folder.

8. Now move everything from the Old System Folder you created in step 2
into the new System folder. If you're asked if you want to replace
anything, you missed something in step 7. You'll need to replace
things individually until you find the duplicate piece. Also
reinstall any fonts or DA's you removed in step 6.

9. Reboot. You should now have a clean, defragmented System file
that takes up less memory and disk space and a much more stable
system overall.


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