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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).
• 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
• The maximum memory speed is determined by the combination of the microprocessor, DIMM speed, and
the number of DIMMs installed in each channel.
• In two-DIMM-per-channel configuration, a server with an Intel Xeon X5600 series microprocessor
automatically operates with a maximum memory speed of up to 1333 MHz when one of the following
conditions is met:
– Two 1.5 V single-rank or dual-rank RDIMMs are installed in the same channel. In the Setup utility,
Memory speed is set to Max performance mode
– Two 1.35 V single-rank or dual-ranl RDIMMs are installed in the same channel. In the Setup utility,
Memory speed is set to Max performance and LV-DIMM power is set to Enhance performance
mode. The 1.35 V RDIMMs will function at 1.5 V
• The server supports a maximum of 18 single-rank or dual-rank RDIMMs. The server supports up to 12
single-rank or dual-rank UDIMMs or quad-rank RDIMMs.
• The server supports three single-rank or dual-rank DIMMs per channel. The server supports a maximum
of two quad-rank RDIMMs per channel. The following table shows an example of the maximum amount of
memory that you can install using ranked DIMMs:
Table 9. Maximum memory installation using ranked DIMMs
Number of DIMMs
12
12
18
18
18
18
System x3550 M3Installation and User's Guide
52
DIMM type
Single-rank UDIMMs
Dual-rank UDIMMs
Single-rank RDIMMs
Dual-rank RDIMMs
Dual-rank RDIMMs
Dual-rank RDIMMs
DIMM size
2 GB
4 GB
2 GB
2 GB
4 GB
8 GB
Total memory
24 GB
48 GB
36 GB
36 GB
72 GB
144 GB
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