IBM B50 - Manual (Page 35)

POST Indicators
If you are using an ASCII terminal (attached to serial port 1), a series of POST
indicators appear on the screen as each subsystem is initialized.
If you are using a directly attached keyboard and a graphical display attached to
a display adapter, then the POST progress indicators appear as icons across the
bottom of the display as follows:
Memory Modules: Tests system memory.
Keyboard: Initializes the keyboard and mouse. When this
icon appears, you can choose one of several different startup
options.
Pressing the F1 key or the numerical 1 key activates the
System Management Services.
Pressing the F5 key or the numerical 5 key invokes the
default boot list mode, located in firmware.
Pressing the F6 key or the numerical 6 key works like the
F5 key or numerical 5 key except firmware looks for a boot
record according to the custom bootlist that was setup by
System Management Services.
Pressing the F8 key or the numerical 8 key selects the
Open Firmware Command line.
If any of these keys are pressed, the chosen option occurs
after all of the POST icons appear. If no keys are pressed, the
server boots from the default boot list and starts the operating
system after all POST icons appear.
Network: Initializes network adapters.
SCSI: Initializes SCSI Adapters.
Chapter 2. Using the Server 2-3