IBM RS/6000 - Manual (Page 93)

4.4.4 Firmware Recovery
During the firmware boot process, one of the first tasks is to verify the Cycle
Redundancy Check (CRC) of the firmware code. If the update portion of the
firmware has a CRC miscompare (is corrupted), you will see the following
symptoms:
One short beep will be sounded on the speaker.
The hard disk LED will blink continuously.
The diskette drive LED is selected or blinking, waiting for a diskette to be
inserted.
The display or tty is blank.
Recovery Procedure: To rewrite the Flash memory, you will need a firmware
recovery diskette.
Note
The recovery diskette must be made in advance at the customer location using
the "Update System Firmware" utility provided with the System Management
Services (SMS) program.
If you have a firmware recovery diskette, perform the following steps:
1. Insert the firmware recovery diskette into the diskette drive. The diskette LED
should turn on while data is being copied into memory.
2. The hard file LED should stop blinking. The system will retry forever when
something is wrong.
3. The system will reboot the machine when the recovery is successful.
The firmware flash routine performs some general clean-up and reboots the
system. Once the system is rebooted, the new flash image is active and executed.
4.4.5 Power-On Self Test (POST)
The following POST tests are performed by the firmware on PCI-based RS/6000
systems:
4.4.5.1 Processor POST
The firmware tests the processor very briefly. If there is a failure, the system will
stop, and the initial beep of the speaker will not be heard.
4.4.5.2 Memory DIMM and L2 Cache POST
The firmware RAM POST tests all the memory; it is done in segments. After the
initial short beep, if the system stops with the hard file indicator on solid, this is the
indication that no memory was found. If some memory is found, then a good 2 KB
continuous segment is sought. If the 2 KB segment cannot be found, the system
stops with the hard file indicator on solid.
The L2 cache is tested. If it fails, there will be a momentary indication when the
display becomes available. The error is also written to the Error Log. During the
system initialization when icons are being displayed for the individual subsystems,
Chapter 4. Boot Support and Firmware 69