HP Server rp7420 HP 9000 rp7420 Server - User Service Guide, Fifth Edition - Page 25

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 9000 rp7420 server is capable of supporting as little as 0.5 GB of main memory using two 256 MB DIMMs installed on a single cell board and as much as 128 GB by filling all 16 DIMM slots on both cell boards with 4 GB DIMMs. DIMMs must be loaded in sets of two at specified locations on the cell board. Two DIMMs are called a rank; two ranks would be equivalent to four DIMMs, three ranks would be six DIMMs, and so on. The DIMMs must be the same size in a rank. 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. For DIMM load order, see Table 1-4. A quad seen in Figure 1-9 is a grouping of four DIMMs. Configurations with 8 or 16 DIMM slots loaded are recommended. The DIMM sizes in a quad can be different but the DIMMs in a rank must be the same size. Table 1-4 DIMM Load Order Number of DIMMs Installed Action Taken 2 DIMMs = 1 Rank 4 DIMMs = 2 Ranks 6 DIMMs = 3 Ranks 8 DIMMs = 4 Ranks 10 DIMMs = 5 Ranks 12 DIMMs = 6 Ranks 14 DIMMs = 7 Ranks 16 DIMMs = 8 Ranks Install First Add Second Add Third Add Fourth Add Fifth Add Sixth Add Seventh Add Last DIMM Location on Cell Quad Location Board 0A and 0B Quad 0 1A and 1B Quad 1 2A and 2B Quad 2 3A and 3B Quad 3 4A and 4B Quad 0 5A and 5B Quad 1 6A and 6B Quad 2 7A and 7B Quad 3 Detailed HP 9000 rp7420 Server Description 25