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POST Code

The Power-on Self Test (POST) software is executed when the computer first boots. This encompasses many of the traditional Macintosh ROM operations and is based on the hardware initialization code used in the past: setup and initialization of the processor and ASICs, a boot beep, an error beep, diagnostics, and transfer to Open Firmware.

A small debugging mini-nub is part of this section. It allows prodding and poking with some MacsBug-like commands. Getting into the debugger nub is not possible using standard user interface input, however.

Failure to boot in POST causes the error beep, optionally entering the mini-nub.