HP ProLiant DL360e Configuring and using DDR3 memory with HP ProLiant Gen8 Ser - Page 15

Figure 5: Idle and Loaded Latencies for various DDR3 DIMMs on 2P HP ProLiant Gen8 servers. Latency (ns) Latency by DIMM type and capacity at 1DPC HP ProLiant Gen8 servers 160 140 120 100 80 Idle Latency 60 Loaded Latency 40 20 0 2 GB 4GB 8GB 4GB 4GB 8GB 8GB 16GB 16GB 32GB 1Rx8 2Rx8 2Rx8 1Rx4 1Rx4 2Rx4 1Rx4 2Rx4 2Rx4 4Rx4 1333 U1333 U 1333 U 1333 R 1600 R 1333 R 1600 R 1333 R 1600 R 1333 L Factors influencing memory throughput Factors affecting memory throughput include the number of memory channels populated, number of ranks on the channel, channel interleaving, and the speed at which the memory runs. Number of memory channels and throughput The largest impact on throughput is the number of memory channels populated. By interleaving memory access across multiple memory channels, the integrated memory controllers are able to increase memory throughput significantly. Optimal throughput and latency are achieved when all 4 channels of each installed CPU are populated identically. As Figure 7 shows, adding a second DIMM to the system (and thus populating the second memory channel) essentially doubles system read throughput. Gains in throughput for each additional DIMM installed are almost linear until all eight memory channels are populated. 15