Intel SE7520BD2 - Manual (Page 26)

Server Board Features
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Intel ® Server Boards SE7520BD2SCSID2, SE7520BD2SATAD2, and
SE7520BD2VD2
Product codes SE7520BD2SCSID2, SE7520BD2SATAD2, and SE7520BD2VD2 include four
banks of DIMMs across two channels. Channel A consists of DIMMs 1A, 2A, 3A, and 4A.
Channel B consists of DIMMs 1B, 2B, 3B, and 4B. Bank 1 (DIMMs 1B and 1A) is closest to the
edge of the server board. DIMMs must be identical within each bank.
The minimum allowed memory is 256 MB, using a single 256 MB DIMM in DIMM slot 1B. The
system operates in single channel when only a single DIMM is installed. The maximum allowed
usable memory is 16 GB of DDR2-400, using 2 GB DIMMs.
DIMMs must meet the following requirements:
ƒ Use only 240-pin, DDR2-400 ECC, registered DIMM modules
ƒ Have a DIMM organization x72 ECC
ƒ Support the following sizes: 256 MB, 512 MB, 1 GB, 2 GB
ƒ A minimum of one 256MB DIMM is required in DIMM socket 1B. This uses single-channel
interleave. However, for dual-channel interleave, providing optimum performance, a minimum
of two DIMMs should be installed in DIMM sockets 1A and 1B. Except for the option of
installing a single DIMM in socket 1B, DIMMs must be installed in pairs and populated as
follows:
DIMM1A and DIMM 1B: Populate these two sockets together first
DIMM 2A and DIMM 2B: Populate these sockets in addition to DIMM 1A and DIMM 2A
if four DIMMs are to be used.
DIMM 3A and DIMM 3B: Populate these sockets after DIMM 1A, DIMM 1B, DIMM 2A,
and DIMM 2B have been populated.
DIMM 4A and DIMM 4B: Populate these sockets after DIMM 1A, DIMM 1B, DIMM 2A,
DIMM 2B, DIMM 3A, and DIMM 3B have been populated.
Memory Mirroring and Memory On-line Sparing
The Intel ® E7520 chipset includes hardware that supports memory mirroring and memory on-line
sparing. Both memory mirroring and memory on-line sparing provide a way to prevent data loss in
case a DIMM fails.
With memory mirroring the system maintains two copies of all data in the memory subsystem. If a
DIMM fails, the data is not lost because the second copy of the data is available from the mirrored
DIMM. The system will not fail due to memory error unless both the primary and the mirrored
copy of the data become corrupt at the same time.
In a mirrored system, the maximum usable memory is one-half of the installed memory, with a
minimum of four DIMMs installed. Since the data is duplicated across DIMMs, it means that up to
four DIMMs are actively in use at any one time. If six 2 GB DIMMs are installed, the maximum
usable memory is 6 GB (three of the installed DIMMs). The remaining three 2 GB DIMMs are used
for mirroring.