Classic Mac M68K Error Codes

Normad Vaporware Inc., August 24, 1992.
Guide to the Original Macintosh Error Codes by Norman King.

It is very hard to service a Macintosh, or figure out what went
wrong. There are many things that can go wrong with a Macintosh. In
fact it is hard to service unless you have access to the codes it
gives. The original Macintosh series was replaced by many newer
models, but many people still use them.

These codes are also used on newer Macintosh systems, but add extra
zeroes to them. For example a 0F 00000001 on a Mac SE would be the
same as a 0F 0001 on an original Macintosh. So I usually truncate
the zeroes anyway. There should be a space between the first error
code and the second part. Just like the IBM, you have to look up
these Macintosh error codes. For an easy to use machine, it is very
hard to support! Also the Macintosh does not use Parity checking
while most IBM machines do use parity checking, so if the system
bombs a lot on your Mac and you suspect it isn’t the software,
chances are it is the RAM.

When the Macintosh starts up, and cannot load the system, it
displays a Macintosh with a sad face on it. Here is a list of Sad
Face Icon codes:

Code Meaning
01 Malfunctioning ROM (Upgrade the ROM)
02 Malfunctioning RAM – Bus test
03 Malfunctioning RAM – Write Test
04 Malfunctioning RAM – Mod3 Test
05 Malfunctioning RAM – Location
0F Exception Testing – See Exception Subcodes

RAM Location Chart:

Subcode Chip Location Bit Subcode Chip Location Bit
001 F5 0 0100 G5 8
002 F6 1 0200 G6 9
004 F7 2 0400 G7 10
008 F8 3 0800 G8 11
0010 F9 4 1000 G9 12
0020 F10 5 2000 G10 13
0040 F11 6 4000 G11 14
0080 F12 7 8000 G12 15

The F and G are co-ordinates of the Macintosh motherboard.
Please consult your manual from Apple to locate these chips.
You also have to know what a BIT is and how memory works and
the correct way to install a RAM chip. Newer Macintosh systems
use the SIMM method of RAM on a small card.

Exception Subcodes (Sad Face 0F errors)

Code Meaning Code Meaning
0001 Bus Error 0008 Trace
0002 Address Error 0009 Line 1010 Error
0003 Illegal Instruction 000A Line 1111 Error
0004 Zero Divide Error 000B Other
0005 Check Instruction 000C Nothing
0006 Traps Instruction 000D Normal
0007 Privilege Violation

On newer Macintosh systems, there will be four extra zeroes on the

In most cases, most Apple Technicians just upgrade the system
anyway. You need it to run current software. Old ROMs in the
Macintosh 128K machine and the 512KE (FATMAC) could only support
1.5 Megabytes with the old ROM chip sets. So System 7.0 won’t work
on the original Macintoshes unless you upgrade them to a Macintosh
Classic or SE. But if you only want to run an older system and
don’t need System 7.0, or think System 7.0 is too buggy, then just
repair your Mac and be happy with it. Remember that after a while,
machines do run down and die, nothing lasts forever. Also System
7.0 requires a hard disk, and each version of 7.0 needs to be set
up for certain Macintosh models, and not all of 7.0 functions will
work the same on every Mac. In my humble opinion, I found that
Windows 3.1 was easier to install on an IBM 386 machine that System
7.0 is to install on a Macintosh. I had always gotten problems with
the drive reading the disks, or configuring it to run on the

Now, here is help when the Mac won’t work properly. Enjoy!
Troubleshooting the Mac:

Symptom Possible Problem Cure
Bell does not Beep Bad Speaker or connector Replace speaker
or connector
Bad analog board Replace board
Bad main board Replace main board
No Display Monitor not turned on Turn monitor on
No signal to monitor Check cables
No power to monitor Check power
Bad monitor Check monitor
Bad main board Replace main board
Drive LEDs do not
come on Bad or loose connector Check or replace
No Power Check power
Disk drive bad Check disk drive
Disk controller chip bad Replace chip
Main board bad Replace main board

Symptom Possible problem Cure
Keyboard does not
work Keyboard not plugged in Plug in keyboard
Keyboard faulty Check keyboard
Keyboard cable or
connector bad Test Cable
Main board bad Replace main board
Cannot load
programs Bad Diskette Try backup
No System (Also could be higher
density than drive
can handle. )
Drive not working Check with diagnostic
software. Replace
drive or check it out
Bad drive cable or
connector Check drive cable and
Bad memory Check memory, replace
if needed.
Bad main board Replace main board
Blinking “X” on
screen No System on disk Check disk on other
Macintosh, replace.
Mouse won’t work Dirt Roller or contacts Clean mouse
Poor rolling surface Try different surface
Mouse is bad Replace mouse
Printer Failure Bad cable or connectors Check cable and
No power to printer Check power
Cover not in place Check cover and
on-line light
DIP switches not set Set Switches
Incompatible printer Use another printer
No Time, date, or
inconsistent Dead Clock Battery Replace Battery.

Here is a list of possible Opening screen Icons for the Mac:

Icon Meaning
Happy Face Everything is fine. (You want this!)
Sad Face Unable to continue, something’s wrong.
X Bad disk, or wrong media type. Super Disk in normal
disk drive?
? Computer is waiting for disk or can’t recognize
current disk. (wrong type? IBM format?)
Clock Wait- program is loading or command being carried
out. Means the Mac is busy doing something.


Here is a list of Maintenance routines to keep your Mac happy and

Daily Routines:
1. Make backup copies of all data diskettes you’ve been using. This
should be done at the end of each session and periodically during
the session. The Mac has no parity checking, and if it bombs, it
could corrupt the data as it was writing it to disk. You will be
happier with a backup just in case the Mac goes Demonic with

Weekly Routines:
1. Give the Mac area a quick clean to cut down on the amount of
dust. If dust gets into the Mac, it won’t be happy and will
malfunction. Keep it clean, use a dust cover when not in use. Buy
one or make one out of plastic material.
2. Make copies of all data diskettes that have been used heavily.
The more you use the diskettes, the more material wears off them.
After a while the data goes bye-bye, and you have unhappy users.
3. Clean disk drive heads, if needed. Most of the time bad disk and
drive problems come from dirty drive heads. You can buy a 3.5 inch
disk drive cleaner from any computer place now. It is a good
investment as it keeps the drives clean and happy.

Monthly Routines:
1. Thoroughly clean the entire area, including the printer. Dust is
very mean to the Macintosh. It confuses it if it gets inside, and
can damage disks and printer parts.
2. Clean disk drive heads. You will really want to do this every
month if the Mac needs it or not, just to be on the safe side.
3. Run a diagnostics program on your system. This is a good way to
tell if anything is about to go wrong. Most bulletin boards have
free shareware diagnostic programs for the Mac, or Mac User groups
can sell you a disk containing diagnostic programs. Check with your
Apple dealer for local user group listings.
4. Test devices and equipment that are rarely used. Murphy’s Law of
computers states that anything that can go wrong usually does,
especially if it isn’t used very often!

Occasional Routines:
1. Test backups already made, and rotate backups to keep the most
current backup in use. Who knows, you might have bought a bad disk
or a backup disk may have been used too much and the media wore
off? The best backup is a tape backup of a hard disk!
2. Make new backups of important programs and data, if needed. Also
make copies of the original disks and store the original disks in
a safe, dustfree place. Like if you buy new software, backup all
the disks and use the backup to install the software. That way you
can always re-copy the originals if the backups go bad. This is a
trick picked up from the IBM world.
3. Spend some time with your diskettes on someone else’s Macintosh.
Hey, you never know if you formatted it as a 400K, 800K, or 1.44
Megabyte Super drive format. Check it out on a friend’s Mac to see
if it works. Original Macs had 400K Single Sided Low Density
drives, the Mac Plus and above used the 800K Double Sided Low
Density drive, and current Macs use the Super Drive to read/write
IBM formats and get 1.44 Megabytes of storage! Find out by
formatting a new disk in your friend’s Mac to see what type of
drive it has. You can check the amount of space by doing an
Information on the disk by double clicking it to display its
contents and kilobytes free (Megabytes in System 7).
4. Learn something new about your system and its programs. Not all
programs work the same. You can always find new ways to do things,
what the certain command keys do, and shortcuts in the menu system.
Ask friends about it if they know any shortcuts.

I hope this text file helps you to use and service your Macintosh
much better than before. These hints I have picked up over the
years in working with computers, and I have applied them to the
Macintosh series. While this file covers the original Macintosh
systems, it can be used for the more recent systems too in most
cases. Also Macintosh systems besides the //FX and Quadra do not
use DMA channels, just a little bit of trivia. And also Sony helps
make Powerbooks, and Sharp helps make the Newton. So Apple works
with more than just IBM in making computers!

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