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
74
MT1864/1865/2525/2526/2527/2528
