System Error (Bomb)
Apple Classic Macintosh
Severity: CriticalWhat Does This Error Mean?
The bomb dialog is the Classic Mac's crash screen — a small bomb icon with an error ID number. It means an application or the system itself encountered an unrecoverable error. You must restart the Mac. The error ID helps identify the cause.
Affected Models
- Macintosh Plus
- Macintosh SE
- Macintosh Classic
- Macintosh II
- Macintosh LC
- Macintosh Quadra
- Power Macintosh (System 7)
- Basilisk II emulator
Common Causes
- Application bug causing an illegal memory access
- Extension conflict — two startup extensions interfering with each other
- Insufficient RAM for the running application
- Corrupt system file or preference file
- Hardware issue — failing hard drive or bad RAM
How to Fix It
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Note the error ID number shown in the bomb dialog.
Common IDs: 01 = bus error, 02 = address error, 03 = illegal instruction, 25 = out of memory, 28 = stack overflow. The ID helps narrow down whether it is a software bug, memory issue, or hardware problem.
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Click Restart (or press the reset button if the dialog is unresponsive).
The bomb dialog sometimes has a Restart button. If the Mac is completely frozen, use the programmer's reset button (a small button with a triangle icon on the side of the Mac) or hold the power button.
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Restart with extensions disabled (hold Shift at startup).
If the crash happens during startup, extension conflicts are a likely cause. Holding Shift disables all extensions in System 7. If the Mac boots cleanly, enable extensions one by one to find the conflict.
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Increase the application's memory allocation if the error is ID 25 (out of memory).
Select the application icon, choose Get Info from the File menu, and increase the Preferred Size under Memory Requirements. Classic Mac OS does not have virtual memory by default — each app gets a fixed memory partition.
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Rebuild the desktop file by holding Command + Option at startup.
A corrupt desktop file can cause crashes and strange behaviour. When prompted to rebuild, click OK. This recreates the file that tracks icons and file-application associations.
Frequently Asked Questions
Why did Apple use a bomb icon for crash screens?
The bomb icon was designed by Susan Kare, the graphic designer behind most of the original Macintosh icons. It was meant to clearly indicate something had gone wrong, in the Mac tradition of using visual metaphors instead of cryptic codes.
What is the difference between a Type 1 and Type 11 error?
Type 1 is a bus error — the CPU tried to access memory that does not exist. Type 11 is a hardware exception — on 68K Macs it often indicates a true hardware fault, while on PowerPC Macs it became a catch-all for many different crash types.