IBM 88772ru User Guide - Page 46

Disabled, Memory, Settings

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v When you install additional DIMMs on a microprocessor/memory card, be sure to install them in pairs. Each pair of DIMMs must be the same speed, type, and size. However, each microprocessor/memory card can have different speed, type, and size DIMMs. v You do not have to save new configuration information when you install or remove DIMMs, unless you replace a DIMM that was marked as Disabled in the Memory Settings menu of the Configuration/Setup Utility program. In this case, you must re-enable the row in the Configuration/Setup Utility program or reload the default memory settings. v When you restart the server after you add or remove a DIMM, the server displays a message that the memory configuration has changed. v Chipkill memory is not supported by 512 MB DIMMs. v Each microprocessor/memory card individually supports Chipkill memory only if all DIMMs on the microprocessor/memory card support Chipkill memory. If any DIMMs on a microprocessor/memory card do not support Chipkill memory, the microprocessor/memory card does not support Chipkill memory. v The server supports online-spare memory. This feature disables the failed memory from the system configuration and activates an online-spare memory 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 size as, or larger than, the largest active DIMM pairs. Enable online-spare memory through the Configuration/Setup Utility program. The online-spare DIMM pairs are assigned according to your DIMM configuration. v Memory scrubbing is an automatic daily test of all the system memory that detects and reports memory errors that might be developing before they cause a server outage. If memory scrubbing determines that a DIMM is damaged beyond use, read and write operations are redirected to the remaining good DIMMs. Memory scrubbing then reports the damaged DIMM and light path diagnostics displays the error. When an error is detected, memory scrubbing determines whether the error is recoverable. If it is recoverable, online-spare memory is enabled and the data that was stored in the damaged locations is rewritten to new locations. The error is then reported so that you can perform preventive maintenance. Provided that there are enough good locations to enable the correct operation of the server, no further action is taken other than recording the error in the error logs. If the error is not recoverable, memory scrubbing causes the server to restart and disables the failing DIMMs after the restart. Also, memory scrubbing records the error and lights LEDs to guide you to the failing DIMM. v See Table 4 for the order in which to install DIMMs on each microprocessor/memory card. Table 4. DIMM pair installation sequence Installation order First pair DIMM connectors 1 and 2 Second pair 3 and 4 Third pair Fourth pair 5 and 6 7 and 8 The following illustration shows the DIMM connectors on the microprocessor/memory card. 34 IBM System x3755 Type 8877: User's Guide

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v
When
you
install
additional
DIMMs
on
a
microprocessor/memory
card,
be
sure
to
install
them
in
pairs.
Each
pair
of
DIMMs
must
be
the
same
speed,
type,
and
size.
However,
each
microprocessor/memory
card
can
have
different
speed,
type,
and
size
DIMMs.
v
You
do
not
have
to
save
new
configuration
information
when
you
install
or
remove
DIMMs,
unless
you
replace
a
DIMM
that
was
marked
as
Disabled
in
the
Memory
Settings
menu
of
the
Configuration/Setup
Utility
program.
In
this
case,
you
must
re-enable
the
row
in
the
Configuration/Setup
Utility
program
or
reload
the
default
memory
settings.
v
When
you
restart
the
server
after
you
add
or
remove
a
DIMM,
the
server
displays
a
message
that
the
memory
configuration
has
changed.
v
Chipkill
memory
is
not
supported
by
512
MB
DIMMs.
v
Each
microprocessor/memory
card
individually
supports
Chipkill
memory
only
if
all
DIMMs
on
the
microprocessor/memory
card
support
Chipkill
memory.
If
any
DIMMs
on
a
microprocessor/memory
card
do
not
support
Chipkill
memory,
the
microprocessor/memory
card
does
not
support
Chipkill
memory.
v
The
server
supports
online-spare
memory.
This
feature
disables
the
failed
memory
from
the
system
configuration
and
activates
an
online-spare
memory
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
size
as,
or
larger
than,
the
largest
active
DIMM
pairs.
Enable
online-spare
memory
through
the
Configuration/Setup
Utility
program.
The
online-spare
DIMM
pairs
are
assigned
according
to
your
DIMM
configuration.
v
Memory
scrubbing
is
an
automatic
daily
test
of
all
the
system
memory
that
detects
and
reports
memory
errors
that
might
be
developing
before
they
cause
a
server
outage.
If
memory
scrubbing
determines
that
a
DIMM
is
damaged
beyond
use,
read
and
write
operations
are
redirected
to
the
remaining
good
DIMMs.
Memory
scrubbing
then
reports
the
damaged
DIMM
and
light
path
diagnostics
displays
the
error.
When
an
error
is
detected,
memory
scrubbing
determines
whether
the
error
is
recoverable.
If
it
is
recoverable,
online-spare
memory
is
enabled
and
the
data
that
was
stored
in
the
damaged
locations
is
rewritten
to
new
locations.
The
error
is
then
reported
so
that
you
can
perform
preventive
maintenance.
Provided
that
there
are
enough
good
locations
to
enable
the
correct
operation
of
the
server,
no
further
action
is
taken
other
than
recording
the
error
in
the
error
logs.
If
the
error
is
not
recoverable,
memory
scrubbing
causes
the
server
to
restart
and
disables
the
failing
DIMMs
after
the
restart.
Also,
memory
scrubbing
records
the
error
and
lights
LEDs
to
guide
you
to
the
failing
DIMM.
v
See
Table
4
for
the
order
in
which
to
install
DIMMs
on
each
microprocessor/memory
card.
Table
4.
DIMM
pair
installation
sequence
Installation
order
DIMM
connectors
First
pair
1
and
2
Second
pair
3
and
4
Third
pair
5
and
6
Fourth
pair
7
and
8
The
following
illustration
shows
the
DIMM
connectors
on
the
microprocessor/memory
card.
34
IBM
System
x3755
Type
8877:
User’s
Guide