The Power On Self Test (POST) is the component of the firmware that starts the Mark 1 when the power is turned on and passes execution to the bootstrap.
The POST sequence is built in to the firmware and cannot be modified.
The Mark 1 boots using the following sequence:
_object sets and broadcasts the "power" and "user" env variables._fw:post resets the display (MK1DISP_RESET_ALL) and starts the POST sequence timer._fw:post requests a datetime broadcast from _fw:clock._fw:post requests the object label from _object._fw:post renders the POST screen and requests RAM info._fw:post starts allocating all RAM to itself for the RAM test._fw:post frees all RAM._fw:post requests the PCI device list._fw:post renders it and starts another timer._fw:post either opens the setup utility (if DEL was pressed) or sends a "start" message to _bootstrap._bootstrap boots the system.