HP ProLiant SL2x170z HP ProLiant SL6000 Scalable System technology - Page 15

Unbuffered and registered DIMMs DDR3 DIMMs are available as both Unbuffered (UDIMMs) and Registered (RDIMMs). Both UDIMMs and RDIMMs support error correcting code (ECC). There are three types of DDR3 memory: • PC3-8500R (RDIMM) -1066 or 800 MT/s data rate, depending on memory configuration and processor • PC3-10600E (UDIMM) -1333, 1066, or 800 MT/s data rate, depending on memory configuration and processor • PC3-10600R (RDIMM) -1333, 1066, or 800 MT/s data rate, depending on memory configuration and processor Administrators can use either RDIMMs or UDIMMs, but RDIMM and UDIMM memory cannot be mixed within a single server. When choosing memory configurations using DDR3 memory, the following guidelines are useful: • UDIMM configurations are limited to a maximum of two UDIMMs per memory channel because the memory controller must drive the address and command signals to each DRAM chip on a channel. This results in a 24 GB maximum configuration. Because they require fewer components, UDIMMs are typically less expensive than RDIMMs. • RDIMM configurations can provide larger memory capacity because the memory controller only drives the address and command signals to a single register chip, thereby reducing the electrical load on the memory controller. Users requiring large memory footprints can install three 8-GB RDIMMs per channel for a total of 144 GB. • For smaller memory configurations, installing only one or two DIMMs per memory channel can potentially increase memory performance. In many instances this allows administrators to clock the memory channel at a higher data rate. Table 1 summarizes the choices available for DDR3 memory. Table 1. DDR3 memory options PC3-8500R Type RDIMM DIMM capacity (GB) 4 PC3-8500R RDIMM 8 PC3-10600R RDIMM 2 PC3-10600R RDIMM 4 PC3-10600R RDIMM 8 PC3-10600E UDIMM 1 PC3-10600E UDIMM 2 Rank quad dual dual dual dual single dual Max. data rate in MT/s (1 or 2 DIMMs/channel 1066 1066 1333 1333 1333 1333 1333 Max. data rate in MT/s (3 DIMMs/channel) 800 800 800 800 800 N/A N/A An RBSU setting allows PC3-10600R memory modules to run at 1333 MT/s with two DIMMs per channel and without performance degradation. Only HP branded DIMMs have been fully validated to operate at this speed. Third-party DIMMs may not meet stringent design requirements; therefore, HP does not recommend configuring third-party DIMMs for 1333 MT/s data rates with two DIMMs per channel. At this writing, operating the memory at 1333 MT/s is supported only on select ProLiant SL G6 server trays using the Xeon 5500 Series processors operating at 95W. 15