IBM 7378 Problem Determination And Service Manual page 251

v When you install or remove DIMMs, the server configuration information
changes. When you restart the server, the system displays a message that
indicates that the memory configuration has changed.
v The server supports only industry-standard double-data-rate 3 (DDR3), 800,
1066, or 1333 MHz, PC3-10600R-999, registered or unbuffered, synchronous
dynamic random-access memory (SDRAM) dual inline memory modules (DIMMs)
with error correcting code (ECC). See http://www.ibm.com/servers/eserver/
serverproven/compat/us/ for a list of supported memory modules for the server.
– The specifications of a DDR3 DIMM are on a label on the DIMM, in the
following format.
ggg eRxff-PC3-wwwwwm-aa-bb-cc
where:
ggg is the total capacity of the DIMM (for example, 1GB, 2GB, or 4GB)
e is the number of ranks
1 = single-rank
2 = dual-rank
4 = quad-rank
ff is the device organization (bit width)
4 = x4 organization (4 DQ lines per SDRAM)
8 = x8 organization
16 = x16 organization
wwwww is the DIMM bandwidth, in MBps
6400 = 6.40 GBps (PC3-800 SDRAMs, 8-byte primary data bus)
8500 = 8.53 GBps (PC3-1066 SDRAMs, 8-byte primary data bus)
10600 = 10.66 GBps (PC3-1333 SDRAMs, 8-byte primary data bus)
12800 = 12.80 GBps PC3-1600 SDRAMs, 8-byte primary data bus)
m is the DIMM type
E = Unbuffered DIMM (UDIMM) with ECC (x72-bit module data bus)
R = Registered DIMM (RDIMM)
U = Unbuffered DIMM with no ECC (x64-bit primary data bus)
aa is the CAS latency, in clocks at maximum operating frequency
bb is the JEDEC SPD Revision Encoding and Additions level
cc is the reference design file for the design of the DIMM
d is the revision number of the reference design of the DIMM
Note: To determine the type of a DIMM, see the label on the DIMM. The
information on the label is in the format xxxxx nRxxx PC3-xxxxx-xx-xx-xxx. The
numeral in the sixth numerical position indicates whether the DIMM is single-rank
(n=1), dual-rank (n=2), or quad-rank (n=4).
v The following rules apply to DDR3 DIMM speed as it relates to the number of
DIMMs in a channel:
– When you install 1 DIMM per channel, the memory runs at 1333 MHz
– When you install 2 DIMMs per channel, the memory runs at 1066 MHz
– When you install 3 DIMMs per channel, the memory runs at 800 MHz
– All channels in a server run at the fastest common frequency
– Do not install registered and unbuffered DIMMs in the same server
Chapter 5. Removing and replacing server components
233