When
you
use
memory
mirroring,
you
must
install
two
pairs
of
DIMMs
at
a
time.
The
four
DIMMs
in
each
group
must
be
identical.
See
the
following
table
for
the
installation
sequence
of
DIMM
connectors
for
memory
mirroring.
Table
3.
Memory
mirroring
DIMM
installation
sequence
Group
DIMM
connectors
1
1,
3,
5,
and
7
2
2,
4,
6,
and
8
Table
4.
Memory
mirroring
DIMM
functions
Group
Active
DIMMs
Mirroring
DIMMs
1
1,
3
5,
7
2
2,
4
6,
8
v
The
server
supports
online-spare
memory.
This
feature
disables
the
failed
memory
from
the
system
configuration
and
activates
an
online-spare
pair
of
DIMMs
to
replace
the
failed
active
DIMM
pair.
Online-spare
memory
reduces
the
amount
of
available
memory.
Before
you
can
enable
this
feature,
you
must
install
up
to
two
additional
pairs
of
DIMMs.
The
online-spare
DIMM
pairs
must
be
the
same
speed,
type,
and
the
same
size
as,
or
larger
than,
the
largest
active
DIMM
pairs.
Enable
online-spare
memory
through
the
Configuration/Setup
Utility
program.
The
BIOS
code
assigns
the
online-spare
DIMM
pairs
according
to
your
DIMM
configuration.
Two
online-spare
configurations
are
supported.
See
for
the
online-spare
memory
DIMM
connector
assignments.
Table
5.
Online-spare
DIMM
connector
assignments
Group
DIMM
connectors
1
1
and
3,
2
and
4
2
5
and
7,
6
and
8
v
You
can
enable
either
online-spare
memory
or
memory
mirroring,
but
not
both
at
the
same
time.
Online-spare
memory
provides
more
memory
capacity
than
mirroring;
mirroring
provides
better
memory
protection
but
less
memory
capacity
than
online-spare
memory.
v
When
you
install
or
remove
DIMMs,
the
server
configuration
information
changes.
When
you
restart
the
server,
the
system
displays
a
message
that
indicates
that
the
memory
configuration
has
changed.
To
install
a
DIMM,
complete
the
following
steps:
1.
Read
the
safety
information
that
begins
on
page
and
2.
Turn
off
the
server
and
peripheral
devices
and
disconnect
the
power
cords
and
all
external
cables,
if
necessary.
3.
Remove
the
server
cover.
Attention:
To
avoid
breaking
the
retaining
clips
or
damaging
the
DIMM
connectors,
open
and
close
the
clips
gently.
4.
Open
the
retaining
clip
on
each
end
of
the
DIMM
connector.
38
IBM
System
x3550
Type
7978:
User’s
Guide
Summary of Contents for 3550 Type 7978
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