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Installing memory modules
Adding memory to your server is an easy way to make programs run faster. You
can increase the amount of memory in your server by installing memory-module
options. When you install memory, you must install a set of two or four matched
dual inline memory modules (DIMMs).
Before you install memory, review the following:
v The DIMM options available for your server are 256 MB, 512 MB, and 1 GB.
v The amount of usable memory will be reduced depending on the system
v Your server comes with a minimum of two 256 MB DIMMs (for a total of 512 MB
v When you install additional DIMMs, be sure to install them in pairs or quads and
v All the DIMMs in a single pair or quad must be the same size, speed, and type.
v Multiple pairs or quads of DIMMs do not have to contain DIMMs of the same
v The memory board contains 12 DIMM connectors and supports two-way and
v Install only 2.5 V, 184-pin, 72-bit, 100 MHz, double-data-rate (DDR), PC1600,
v Installing or removing DIMMs changes the configuration information in the server.
v Your server supports the Hot Spare Memory feature in the event of an active
12
IBM xSeries 255 Type 8685: Installation Guide
Your server supports a minimum of 512 MB and a maximum of 12 GB of system
memory.
configuration. A certain amount of memory must be reserved below the amount
of installed memory for system resources. The BIOS will display the amount of
installed memory.
memory) installed in the DIMM 2 and DIMM 8 memory connectors (D2 and D8,
respectively). You must have DIMMs installed in these connectors at all times.
follow the DIMM installation sequence in the illustration in this section. A pair or
quad is also known as a memory bank. See Table 2 on page 13 for the DIMM
connectors in each pair or quad.
size, speed, and type, unless the Hot Spare Memory feature is enabled.
four-way memory interleaving.
To use the four-way memory interleaving technology in your server, you must
install DIMMs in all four connectors in each populated set.
registered synchronous dynamic random-access memory (SDRAM) dual inline
memory modules (DIMMs) with error correcting code (ECC). Only 100 MHz,
72-bit, registered, synchronous memory is supported for the 256 MB, 512 MB,
and 1 GB DIMMs. These DIMMs must be compatible with the latest PC1600
SDRAM Registered DIMM specification. For a list of supported options for your
server, go to http://www.ibm.com/us/compat/ on the World Wide Web.
The Configuration/Setup Utility program automatically saves the new
configuration information. When you restart the server, the system displays a
message indicating that the memory configuration has changed. See the User's
Guide on the IBM xSeries Documentation CD for more information about the
Configuration/Setup Utility program.
memory pair or quad of DIMM failure. This feature, when enabled, disables the
failed memory from the system configuration and activates a Hot Spare Memory
pair or quad of DIMMs to replace the failed pair or quad of DIMMs. Before you
can enable this feature, you must also install at least one additional pair or quad
of DIMMs as described in this book. To ensure proper server operation and to
avoid disabling the Hot Spare Memory feature, all additional pairs or quads of
DIMMs must be the same size, speed, and type as the failed pair or quad of
DIMMs.
You can enable the Hot Spare Memory feature through the Configuration/Setup
Utility program. After you enable the Hot Spare Memory feature, the
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