HP ProLiant DL360e Configuring and using DDR3 memory with HP ProLiant Gen8 Ser - Page 21

Figure 11: Power by memory speed using 8 x 8GB DIMMs installed at 1DIMM per channel. Total memory power consumption 8GB DIMMs installed at 1 DIMM per channel 50 45 40 35 30 25 20 15 10 5 0 8 GB 2R UDIMMs 1333 8 GB 2R RDIMMs 1333 8 GB 1R RDIMMs 1600 Idle Power (W) Loaded Power (W) General guidelines when optimizing for power consumption When optimizing for lowest power consumption, you can use the following general rules. • If your memory size requirements can be met, use UDIMMs instead of RDIMMs. With their additional memory channels, you can configure 2P ProLiant Gen8 servers up to 128 GB using UDIMMs. • Use the smallest number of DIMMs possible, by using the highest capacity DIMM. • For additional power savings with any memory configuration, you should run memory at the slowest speed possible. With HP ProLiant Gen8 servers, this is 800 MT/s. Optimizing for Resiliency DDR3 DIMMs may be constructed using either 4-bit wide (x4) or 8-bit wide DRAM chips. Current ECC algorithms used in the memory controllers are capable of detecting and correcting memory errors up to 4 bits wide. For DIMMS constructed using x4 DRAMs, this means that an entire DRAM chip on the memory module can fail without causing a failure of the module itself. DIMMs constructed using x8 DRAMs cannot tolerate the failure of DRAM chip. The ECC algorithm can detect the failure, but it cannot correct it. As a result, systems configured with DIMMs using x4 DRAMs are safer from potential memory failures than those using memory consisting of x8 DRAMs. While all UDIMMs are made with x8 DRAMs, RDIMMs and LRDIMMs may be constructed with x4 or x8 DRAMs. To provide the highest levels of availability and resiliency for ProLiant Gen8 servers, all HP SmartMemory RDIMMs and LRDIMMs are constructed using x4 DRAMs only. 21