IBM 6C4 - Manual (Page 196)

cd /usr/lpp/diagnostics/bin
./update_flash -f /tmp/fwupdate/RRyymmdd.img
Attention: Do not overlook the periods (.) in the commands shown above. AIX
commands are case-sensitive. Type them exactly as shown.
You will be asked for confirmation to proceed with the firmware update and the required
reboot. If you confirm, the system will apply the new firmware, reboot, and return to the
AIX prompt. This may take up to ten minutes depending on the configuration of the
system.
Attention: On some systems, the message Wait for rebooting before stopping
may display on the system console. Do not turn off the system until the system has fully
rebooted to the AIX login prompt. If a shutdown is necessary at that time, log in as root
user and issue the shutdown command.
While the update is in progress, you will see Rebooting... on the display for several
minutes.
The firmware update is complete.
178 pSeries 630 Model 6C4 and Model 6E4 User’s Guide