This section describes the server memory subsystem.
For more information about system memory (including DIMM population rules) and MR cards, see: Memory Riser Card and DIMM Reference
System memory resides on memory riser (MR) cards. Each card has 12 DIMM slots. The slot capacity of the server depends on the number of MR cards in the server, which in turn depends on the number of CPUs in the server. The server is available in a two CPU configuration and a four CPU configuration. Each CPU requires two MR cards. Therefore, a two-CPU configuration has 48 slots (four MR cards) and a four-CPU configuration has 96 slots (eight MR cards).
MR cards contain twelve DIMM slots, four DDR3 channels, and two memory buffer ASICs. Each memory buffer has two channels (A and B) and links to three DIMM slots per channel. Each memory buffer is connected to the processor's built-in memory controller by an SMI-2 link.
For balanced performance, each channel for each memory buffer on the MR card must be populated. The only exception supported is a minimum factory configuration of two 16 GB DIMMs per MR card in DIMM slots D0 and D3.