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Restoring the serial number of the system
unit
When the computer was manufactured, the EEPROM on
the system board was loaded with the serial numbers of
the system and all major components. These numbers
need to remain the same throughout the life of the
computer.
If you replace the system board, you must restore the
serial number of the system unit to its original value.
Before replacing the system board, save the original serial
number by doing the following:
1. Install the ThinkPad hardware maintenance diskette
version 1.61, and restart the computer.
2. From the main menu, select 1. Set System
Identification.
3. Select 2. Read S/N data from EEPROM.
The serial number for each device is displayed. Write
down the serial number of the system unit, designated as
follows:
20: System unit serial number
After you have replaced the system board, restore the
serial number by doing the following:
1. Install the ThinkPad hardware maintenance diskette
version 1.61 and restart the computer.
2. From the main menu, select 1. Set System
Identification.
3. Select 1. Add S/N data from EEPROM.
Follow the instructions on the screen.
Note: The serial number of the system unit is written on
the label attached on the bottom of the computer.
Retaining the UUID
The Universally Unique Identifier (UUID) is a 128-bit
number uniquely assigned to your computer at production
and stored in the EEPROM of your system board. The
algorithm that generates the number is designed to provide
unique IDs until the year A.D. 3400. No two computers in
the world have the same number.
When you replace the system board, you must set the
UUID on the new system board as follows:
1. Install the ThinkPad hardware maintenance diskette
version 1.61, and restart the computer.
2. From the main menu, select 4. Assign UUID.
A new UUID is created and written. If a valid UUID
already exists, it is not overwritten.
FRU replacement notices
ThinkPad A21e 49