The four-channel Double Data Rate (DDR2) memory interface on the MCXT and MCXI SHBs supports up to 16GB of Fully Buffered DIMM (FB-DIMM) memory; the MCXT-E and MCXI-E models support up to 32GB of FB-DIMM memory.

FB-DIMMs have "Advanced Memory Buffer" chips that provide enhanced signal integrity and improved error detection that help reduce soft memory errors. FB-DIMM memory technology improves overall system reliability by extending the current ECC capability to include protection of command and address data. FD-DIMMs feature automatic retries when a memory error is detected, which results in uninterrupted system operation in the event of transient errors.

An MCX-series SHB uses industry standard 72-bit wide ECC gold finger FB-DIMM memory modules in four (MCXT/MCXI) or eight (MCXT-E/MCXI-E) 240-pin sockets. The FB-DIMMs must be PC2-4200 or PC2-5300 (DDR2-533 or DDR2-667) and comply with the JEDEC Rev. 2.0 specifications.

The following dual-rank FB-DIMM sizes are supported:

FB-DIMM Size	DIMM Type	ECC
512MB	Registered	64M x 72
1GB	Registered	128M x 72
2GB	Registered	256M x 72
4GB	Registered	512M x 72

A minimum of one 512MB FB-DIMM is required and must be populated in DIMM socket BK0A.

NOTE: With the bracket end of the board to the right, the four FB-DIMM sockets available on the MCXT and MCXI SHBs are numbered BK0A, BK1A, BK0B and BK1B, from top to bottom. On the extended-memory MCXT-E and MCXI-E SHBs, there are an additional four FB-DIMM sockets. The upper sockets are BK2A and BK2B, from left to right, and the lower sockets are BK3A and BK3B. These socket definitions are illustrated in the board layouts. All memory modules must have gold contacts.

NOTE: To maximize memory interface speed and bandwidth, and to take full advantage of the four-channel memory interface of the SHB's memory controller hub, the FB-DIMMs in socket banks 0A and 1A must be identical with respect to manufacturing, speed, timing and organization. Likewise, FB-DIMMs used in sockets 0B and 1B must be identical. FB-DIMMs in socket banks contained within the same memory channel, i.e., 0A and 2A do not have to be identical.

A minimum of one 512MB FB-DIMM is required and must be populated in DIMM socket BK0A. When using more that one FB-DIMM, you must populate the memory sockets in multiples of two in order to maximize the speed and performance of the memory interface. The following table explains the DDR2 FB-DIMM population rules:

FB-DIMM POPULATION CONFIGURATION	FB-DIMM Sockets (MCXT, MCXE)				FB-DIMM Sockets (MCXT-E, MCXI-E)
	BANK 0A	BANK 1A	BANK 0B	BANK 1B	BANK 2A	BANK 2B	BANK 3A	BANK 3B
Single Module	FB-DIMM	Empty	Empty	Empty	Empty	Empty	Empty	Empty
Two Modules	FB-DIMM	FB-DIMM	Empty	Empty	Empty	Empty	Empty	Empty
Four Modules	FB-DIMM	FB-DIMM	FB-DIMM	FB-DIMM	Empty	Empty	Empty	Empty
Six Modules	FB-DIMM	FB-DIMM	FB-DIMM	FB-DIMM	FB-DIMM	FB-DIMM	Empty	Empty
Eight Module	FB-DIMM	FB-DIMM	FB-DIMM	FB-DIMM	FB-DIMM	FB-DIMM	FB-DIMM	FB-DIMM