HP Integrity rx7620 Site Preparation Guide, Fourth Editon - HP Integrity rx762 - Page 25

Introduction Detailed HP Integrity rx7620 Server Description The HP Integrity rx7620 Server supports DIMMs with densities of 64, 128, 256, and 512 Mb for the SDRAM devices. Table 1-3 shows each supported DIMM size, the resulting total system capacity, and the memory component density. Each DIMM is connected to two buffer chips on the cell board. DIMMs must be loaded in sets of four at specific locations. For best performance, HP recommends loading sets of eight DIMMs. Table 1-3 HP Integrity rx7620 Server DIMMs DIMM Size 256 MB 512 MB 1 GB 2 GB 4 GB Total Capacity 8 GB 16 GB 32 GB 64 GB 128 GB Memory Component Density 64 megabit 128 megabit 256 megabit 512 megabit 1024 megabit Main Memory Performance Latency to main memory is an important parameter in determining overall system performance. With memory buses running at 125 MHz, the latency for a page hit is 8.5 cycles (68 ns), the latency for a page closed is 11.5 cycles (92 ns), and the latency for a page miss is 14.5 cycles (116 ns). Valid Memory Configurations The HP Integrity rx7620 Server is capable of supporting as little as 0.5GB of main memory using two 256MB DIMMs installed on one of the cell boards and as much as 64 GB by filling all 16 DIMM slots on both cell boards with 2GB DIMMs. DIMMs must be loaded in sets of two at specified locations on the cell board. Two DIMMs are called an "echelon", so two echelons would be equivalent to four DIMMs, three echelons would be equivalent to six DIMMs and so on. The DIMMs must be the same size in an echelon. The DIMMs across all cells in a partition should have identical memory loaded. Figure 1-9 shows the DIMM slot layout on the cell board. See Table 1-4 for DIMM load order. Chapter 1 11