IBM eServer xSeries 455 Type 8855 Hardware Maintenance Manual And Troubleshooting Manual page 106

v Each DIMM in a pair must be of the same size and technology to ensure that the
v You can configure your server to use memory mirroring and memory scrubbing.
v When using memory mirroring, you must install two pairs of DIMMs at a time.
v You can replace a failed DIMM while the server is on, provided that you have
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IBM xSeries 455 Type 8855: Hardware Maintenance Manual and Troubleshooting Guide
server will operate properly. For example, 1 GB DIMMs made from 512 Mb
memory chips may not be paired with 1 GB DIMMs made from 1 Gb memory
chips.
For detailed information about configuring your server and using these features,
see the User's Guide on the IBM xSeries Documentation CD.
The four DIMMs in each bank must be identical. The following table shows the
pairs that are in each bank. See Table 9 on page 95 for the DIMM connector pair
assignments.
Table 10. Memory mirroring DIMM installation sequence
Bank DIMM pairs
1 1 and 2
2 3 and 4
3 5 and 6
4 7 and 8
enabled memory mirroring and that you have installed all DIMMs in the sequence
to support memory mirroring.
If a problem with a DIMM is detected, light path diagnostics will light the
system-error LED on the front of the server, indicating that there is a problem
and guide you to the defective DIMM. When this occurs, first identify the
defective DIMM; then, remove and replace the DIMM. See "Hot-replacing
DIMMs" on page 98 for instructions.
The following illustration shows the LEDs on the DIMM access door:
Port 1 power LED Memory hot-plug
enabled LED
Port 1 power LED: When this LED is off, it indicates that power is removed from
the port and that you can replace a failed DIMM.
Memory hot-plug enabled LED: When this LED is lit, it indicates that hot-swap
memory is enabled. When this LED is flashing, it indicates that data is being
mirrored on the replacement DIMMs.
Port 2 power LED: When this LED is off, it indicates that power is removed from
the port and that you can replace a failed DIMM.
Bank DIMM pairs
5 9 and 10
6 11 and 12
7 13 and 14
Port 2 power LED