IBM RS/6000 - Manual (Page 101)

With the introduction of the E20 came a new electronic key-switch function. As
with the 43P, there is no physical key, but there is a static electronic key. The
key-switch abstraction is set by the firmware at boot time. The provision of the
electronic key is essential for the machine to boot AIX diagnostics from hard disk,
which both the 40P and 43P are unable to do.
5.1.2 Function Keys - Key-Switches at Boot Time
During the boot process, function keys can be pressed to alter the electronic
key-switch and determine which Boot List to use during the boot procedure. There
are four function keys that can be pressed which determine the type of boot which
will occur, these are described as follows:
F1 Key:
F1, when operated from a directly attached keyboard, will invoke the SMS GUI
interface. The electronic key-switch will be set to Normal mode.
F4 Key (4 with an ASCII terminal):
F4, when operated from a directly attached keyboard, will invoke the SMS program
and present the ASCII interface. The electronic key-switch " is set to Normal mode.
F5 Key (5 with ASCII terminal):
The F5 key will cause the default firmware Boot List to be used. The electronic
key-switch is set to Service mode. This mode attempts to boot from the first device
of each found in the list. It does not search for other bootable devices of that type
if the first device is not bootable. Instead, it continues to the next device type in the
list. If after one pass through the Boot List no boot record is found, the firmware
will invoke the SMS program.
Mksysb Booting
To boot from a tape (to restore a mksysb or boot into maintenance mode)
requires SMS. From SMS, you can select an alternative boot device which
includes a tape drive if one is installed.
F6 Key (6 with ASCII terminal)
When F6 is selected, the firmware looks for a boot record according to the custom
Boot List that was set up by SMS or by using the
bootlist command. If the Boot
List was not customized, the default Boot List is used. The electronic key-switch is
set to Service mode. Again, if after a pass through the custom boot list no boot
record is found, the firmware will invoke the SMS program.
When AIX V4.1.4 is installed on the E20 and F30, it automatically sets the
customized Boot List to the installed hard disk. The customized Boot List is
thereafter used by the system when booting in Normal mode, or you can invoke the
customized Boot List in Service mode by pressing F6 during the firmware boot
process.
Chapter 5. AIX Version 4.1.4 Support 77