Lenovo T420i manual Retaining the UUID, Reading or writing the ECA information, MTM on rear label

MTM on rear label:	TTTT-CTO S/N SSSSSSS
Product ID on rear label:	TTTT-MMM (Use this number when setting Serial
	Number)

In the example, the Serial Number to be input is “1STTTTMMMSSSSSSS”.

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 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 simplifies 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 reflect 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 59