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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 LENOVO ThinkPad Hardware Maintenance Diskette Version 1.76 or later, 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.
Reading or writing the ECA information
Information on Engineering Change Announcements (ECA) are stored in the EEPROM of the system board.
The electronic storage of this information simplies the procedure to check if the ECA has been previously
applied to a machine. The machine does not need to be disassembled to check for the ECA application.
To check what ECAs have been previously applied to the machine, use the ECA Information Read/Write
function on the LENOVO ThinkPad Hardware Maintenance Diskette Version 1.76 or later.
1. Insert the LENOVO ThinkPad Hardware Maintenance Diskette Version 1.76 or later, and restart the
computer.
2. From the main menu, select 6. Set ECA Information.
3. To read ECA information, select 2. Read ECA/rework number from EEPROM and follow the
instruction.
4. To read box build date, select 5. Read box build date from EEPROM, and follow the instruction on
the screen.
After an ECA has been applied to the machine, the EEPROM must be updated to reect the ECA's
application. Use the LENOVO ThinkPad Hardware Maintenance Diskette Version 1.76 or later to update the
EEPROM.
Note: Only the ECA number is stored in the EEPROM. The machine type of the ECA is assumed be the same
as the machine type of the machine that had the ECA applied to it.
1. Insert the LENOVO ThinkPad Hardware Maintenance Diskette Version 1.76 or later, and restart the
computer.
2. From the main menu, select 6. Set ECA Information.
3. To write ECA information, select 1. Write ECA/rework number from EEPROM, and follow the
instruction.
4. To write box build date, select 4. Write box build date from EEPROM, and follow the instruction on
the screen.
If the system board is being replaced, try to read the ECA information from the old system board and transfer
the information to the new system. If the system board is inoperable, this will not be possible.
Chapter 7. FRU replacement notices 55