Lenovo System x3250 M5 Installation And Service Manual page 183

• 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
Notes:
1. To determine the type of a DIMM, see the label on the DIMM. The information on the label is in the
format xGB nRxx PC3v-xxxxxx-xx-xx-xx. The numeral in the sixth numerical position indicates
whether the DIMM is single-rank (n=1) or dual-rank (n=2).
2. The amount of usable memory is reduced, depending on the system configuration. A certain
amount of memory must be reserved for system resources. To view the total amount of installed
memory and the amount of configured memory, run the Setup utility. For additional information, see
"Configuring the server" on page 86.
The following illustration shows the location of the DIMM connectors on the system board.
Figure 96. The location of the DIMM connectors on the system board
The following sections provide additional information specific to unbuffered and registered DIMMs that
you must consider.
Unbuffered DIMMs (UDIMMs)
The following notes provide information that you must consider when you install UDIMMs.
• The memory channels run at the lowest common frequency of the DIMMs installed.
• The UDIMM options that are available for the server are 1 GB, 2 GB, 4 GB, and 8 GB (when available)
DIMMs.
• The server supports up to two single-rank or dual-rank UDIMMs per channel.
• The following table lists the supported UDIMM population.
.
Chapter 6 Removing and replacing server components
169