Installing Memory Modules - IBM eServer xSeries 255 Installation Manual

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:
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IBM xSeries 255 Type 8685:Installation Guide
The DIMM options available for your server are 256 MB, 512 MB, and 1GB. Your
server supports a minimum of 512 MB and a maximum of 12GB of system mem-
ory.
The amount of usable memory will be reduced depending on the system configu-
ration. 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.
Your server comes with a minimum of two 256 MB DIMMs (for a total of 512 MB
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.
When you install additional DIMMs, be sure to install them in pairs or quads and
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 con-
nectors in each pair or quad.
All the DIMMs in a single pair or quad must be the same size, speed, and type.
Multiple pairs or quads of DIMMs do not have to contain DIMMs of the same size,
speed, and type, unless the Hot Spare Memory feature is enabled.
The memory board contains 12 DIMM connectors and supports two-way and 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.
Install only 2.5 V, 184-pin, 72-bit, 100 MHz, double-data-rate (DDR), PC1600, reg-
istered synchronous dynamic random-access memory (SDRAM) dual inline mem-
ory modules (DIMMs) with error correcting code (ECC). Only 100MHz, 72-bit,
registered, synchronous memory is supported for the 256 MB, 512 MB, and 1GB
DIMMs. These DIMMs must be compatible with the latest PC1600 SDRAM Regis-
tered DIMM specification. For a list of supported options for your server, go to
http://www.ibm.com/us/compat/ on the World Wide Web.
Installing or removing DIMMs changes the configuration information in the server.
The Configuration/Setup Utility program automatically saves the new configura-
tion information. When you restart the server, the system displays a message indi-
cating that the memory configuration has changed. See the User's Guide on the
IBM xSeries Documentation CD for more information about the Configura-
tion/Setup Utility program.
Your server supports the Hot Spare Memory feature in the event of an active
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 Configura-
tion/Setup Utility program assigns the Hot Spare Memory bank according to your
server configuration. If your server has a two-way interleaved configuration, the