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  1.71  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  ThinkPad  Hardware  Maintenance  Diskette  Version  1.71 
or  later. 
1.  Insert  the  ThinkPad  Hardware  Maintenance  Diskette 
Version  1.71  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  ThinkPad  Hardware  Maintenance 
Diskette  Version  1.71  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  ThinkPad  Hardware  Maintenance  Diskette 
Version  1.71  or  later,  and  restart  the  computer. 
2.  From  the  main  menu,  select  6.  Set  ECA  Information. 
FRU  replacement  notices 
ThinkPad  X40  73