IBM x3250 M3 Problem Determination And Service Manual page 171

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
8500 = 8.53 GBps (PC3-1066 SDRAMs, 8-byte primary data bus)
10600 = 10.66 GBps (PC3-1333 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
Notes:
1. 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) 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 193.
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:
v The memory channels run at the fastest common frequency of the DIMMs
installed.
v Do not mix UDIMMs and RDIMMs in the same server.
v Using ECC and non-ECC UDIMMs in the server will cause the server to run in
non-ECC mode.
v The UDIMM options that are available for the server are 1 GB, 2 GB, and 4 GB
DIMMs.
v You can install a maximum of 16 GB of memory in some server models when
you use UDIMMs.
v The server supports up to two single-rank or dual-rank UDIMMs per channel.
v DIMM slots 3 and 6 are not supported when you install UDIMMs in the server.
Do not install DIMMs in these connectors.
v The following table lists the DIMM support compatibility.
Chapter 5. Removing and replacing server components
153