GURU-MEDITATION
1 INTRODUCTION
If you have been programming the Amiga for a while you have
most certainly seen your nice Amiga blow up in front of your
eyes. However, the Amiga is a nice computer, and if it crashes
it will try to do that as neatly as possible. You are usually
(!) allowed to save any important files, and when the Amiga
goes down it will give you a last message, trying to tell you
what went wrong.
Many programmers have not realized how important that last
message is. For them, it is just a collection of strange
numbers. But those numbers can actually tell you what exactly
went wrong, and once you know what went wrong, it is usually
no problem to find the bug.
2 AMIGA CRASHING
When the Amiga is crashing it happens that the Exec have
realized that something will go wrong and halted that task.
Exec will then open a System requester with a warning message:
Software error - task held
Finish all disk
activity
Select CANCEL to reset/debug |
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You can then save any important files to a disk before you
answer the requester (once you have pressed CANCEL the Guru
will visit you!). Important, since the Amiga is in trouble
it can crash any second, and if you were saving anything onto
a disk at that moment, the disk may become corrupted, and all
data lost. The best solution is to have an empty emergency
disk that you only use when the Amiga is upset. Sometimes the
Exec have not been able to halt the task, and the Guru will
immediately visit you.
3 GURU ALERTS
Once the Amiga really crashes, the powerlight will flash for
some seconds, and an Alert will be activated. For example:
Software failure! Press left mouse button to
continue.
Guru Meditation #84010007.00C13870 |
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Now you only need to decode the message and you have found
the error. (Advanced programmer can attach a modem to the
Amiga and use a program called ROMWack in order to debug the
computer. But we will not discuss it here.)
4 GURU MEDITATION NUMBERS
There exist two different types of Guru Meditation Numbers:
- CPU Errors (680x0 Processor Traps)
- System Software Errors
5 CPU ERRORS
CPU Errors look like this:
Guru Meditation #0000000x.yyyyyyyy
x is one of the following values:
| 2 | Bus Error | Hardware error |
| 3 | Address Error | Word access on odd byte
boundary |
| 4 | Illegal Instruction | |
| 5 | Divide by zero | |
| 6 | CHK Instruction | |
| 7 | TRAPV Instruction | |
| 8 | Privilege Violation | |
| 9 | Trace | |
| A | Opcode 1010 Emulation | Instruction word with a value
between A000-AFFF. |
| B | Opcode 1111 Emulation | Instruction word with a value
between F000-FFFF. |
yyyyyyyy is the address of the task which went wrong. (It
is normally your own program that caused the problem.)
If you get a Guru Meditation number like #00000005.00C13870
it means: A program, at the address C13870, tried to devide
a value by zero. Since you now know what the error was you
only need to look at the places where your program can be
forced to divide a value by zero, and it should not take to
long time to find the bug.
6 SYSTEM SOFTWARE ERRORS
System Software errors look like this:
Guru Meditation #aabbcccc.dddddddd
The first field of the number tells us if the error is a
Recoverable Error or if it is a Dead End Alert. If the error
is a Dead End Alert the number will start with 8 otherwise it
is 0. (The total screen will also be black, while on
Recoverable Errors the screen is merely pushed down a bit.)
The first field of the number tells us also which Device,
Library or Resource went wrong:
LIBRARIES:
| 01 | Exec Library |
| 02 | Graphics Library |
| 03 | Layers Library |
| 04 | Intuition Library |
| 05 | Math Library |
| 06 | CList Library |
| 07 | AmigaDOS Library |
| 08 | RAM Handler Library |
| 09 | Icons Library |
DEVICES:
| 10 | Audio Device |
| 11 | Console Device |
| 12 | GamePort Device |
| 13 | Keyboard Device |
| 14 | Trackdisk Device |
| 15 | Timer Device |
RESOURCES:
| 20 | CIA Resource |
| 21 | Disk Resource |
| 22 | Misc Resource |
OTHERS:
| 30 | BootStrap |
| 31 | Workbench |
| 32 | Disk Copy |
A number like 04 means: Recoverable Error in the Intuition
Library. While a number like 84 means: Fatal Error in
the Intuition Library.
The second field (bb) of the Guru Meditation number gives
us the general cause of the problem:
| 01 | No Memory |
| 02 | Unable to Create Library |
| 03 | Unable to Open Library |
| 04 | Unable to Open Device |
| 05 | Unable to Open Resource |
| 06 | Input/Output (I/O) Error |
| 07 | No Signal |
So a number like 8201cccc means a fatal error in the Graphics
Library, the problem was caused by not enough memory.
The last field (cccc) before the dot gives some more specific
information. Here is a list of some common Guru Meditation
Numbers: (This information is taken form the headerfile
"exec/alerts.h" [V1.3]:)
Exec Library:
| 01000000 | |
| 81000001 | 68000 exception vector checksum |
| 81000002 | Execbase checksum |
| 81000003 | Library checksum failure |
| 81000004 | No memory to make library |
| 81000005 | Corrupted memory list |
| 81000006 | No memory for interrupt servers |
| 81000007 | InitStruct() of an APTR source |
| 81000008 | A semaphore is in illegal state |
| 81000009 | Freeing memory already freed |
| 8100000A | Illegal 68k exception taken |
Graphics Library:
| 02000000 | |
| 82010000 | Graphics out of memory |
| 82010006 | Long frame, no memory |
| 82010007 | Short frame, no memory |
| 02010009 | Text, no memory for TmpRas |
| 8201000A | BltBitMap, no memory |
| 8201000B | Regions, memory not available |
| 82010030 | MakeVPort, no memory |
| 82011234 | Emergency memory not available * |
Layers Library:
| 03000000 | |
| 83010000 | Layers out of memory |
Intuition Library:
| 04000000 | |
| 84000001 | Unknown gadet type |
| 04000001 | Recovery form of AN_GadgetType |
| 84010002 | Create port, no memory |
| 04010003 | Item plane alloc, no memory |
| 04010004 | Sub alloc, no memory |
| 84010005 | Plane alloc, no memory |
| 84000006 | Item box top < RelZero |
| 84010007 | Open screen, no memory |
| 84010008 | Open screen, raster alloc, no memory |
| 84000009 | Open sys screen, unknown type |
| 8401000A | Add SW gadgets, no memory |
| 8401000B | Open window, no memory |
| 8400000C | Bad State Return entering Intuition |
| 8400000D | Bad Message received by IDCMP |
| 8400000E | Weird echo causing incomprehension |
| 8400000F | Couldn't open the Console Device |
Amiga DOS Library:
| 07000000 | |
| 07010001 | No memory at startup |
| 07000002 | EndTask didn't |
| 07000003 | Qpkt failure |
| 07000004 | Unexpected packet received |
| 07000005 | Freevec failed |
| 07000006 | Disk block sequence error |
| 07000007 | Bitmap corrupt |
| 07000008 | Key already free |
| 07000009 | Invalid checksum |
| 0700000A | Disk Error |
| 0700000B | Key out of range |
| 0700000C | Bad overlay |
RAM Library:
| 08000000 | |
| 08000001 | No overlays in library seglists |
Trackdisk Device:
| 14000000 | |
| 14000001 | Calibrate: seek error |
| 14000002 | Delay: error on timer wait |
Timer Device:
| 15000000 | |
| 15000001 | Bad request |
| 15000002 | Power supply does not supply ticks |
Disk Resourcek.resource:
| 21000000 | |
| 21000001 | Get unit: already has disk |
| 21000002 | Interrupt: no active unit |
BootStrap:
| 30000000 | |
| 30000001 | Boot code returned an error |
The number after the dot (dddddd dd) can be three things:
- Address of the task which went wrong.
- If the error occured because of some sort of memory
allocation/deallocation, it is the address of that memory
block.
- If Exec is realy confused the number is 48454C50, which
stands for HELP. (48=H, 45=E, 4C=L, 50=P)
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