Service Reference Guide

Service Reference Guide 11–3
Removal and Replacement Procedures Expansion Cards and Memory
■ DIMMs should be installed in pairs.
■ Do not mix DIMMs of different memory speeds. Performance will reflect the speed of the
slowest DIMM.
■ Each DIMM within a pair should be identical in size. For example, a 256MB DIMM must be
paired with a similar 256MB DIMM.
■ Each DIMM within a pair should be identical in technology. For example, you cannot mix a
256 MB 9-device DIMM with a 128MB 18-device DIMM on the same channel.
✎
To identify which DIMM technology you are using, compare the memory size and number of
DRAM components on the module. A 128 MB DIMM has 18 DRAM components that fully
populate both sides of the module. A 256MB DIMM has 9 DRAM components; four on one side,
five on the other.
■ The first pair of DIMMS should be installed in slots 1 and 2. The DIMM slots are numbered
sequentially. Slot 1 is closest to the CPUs.
■ The second pair of DIMMS, if any, should be installed in slots 3 and 4.
■ DIMMs must be installed correctly. Be sure to match the keyed slot on the DIMM with the
tab on the DIMM socket.
■ For optimal system performance, DIMMs should be installed in identical pairs in the
following three configurations: slot 1 and 2, slot 3 and 4, or all DIMM slots populated in
paired format.
■ If you are using a single DIMM configuration, the DIMM should be installed in slot 1 or slot
3.
✎
Although a single-DIMM configuration is possible, it does not provide the optimal system
performance that a dual-DIMM (dual-channel) of matching sizes, configuration provides.
■ If you are installing two DIMMs of different sizes, they can only be installed in slot 1 and
slot 3 with each DIMM occupying either slot.
✎
Although a mixed size dual-DIMM configuration is possible, it does not provide the optimal
system performance that a dual-DIMM (dual-channel) of matching sizes, configuration provides.
■ No other memory configurations are supported. Attempts to install memory in other
configurations will result in unpredictable system performance.
✎
The following table provides acceptable pairing configurations but do not cover all module
capacities. However, the same pairing configuration applies regardless of the module type and
capacity.