HP Integrity rx7620 Server - User Service Guide, Sixth Edition

Figure 1-8 CPU Locations on the Cell Board
DIMMs
The memory DIMMs used by the HP Integrity rx7620 Server are custom-designed by HP and
are identical to those used in the Superdome server. Each DIMM contains SDRAM memory
components and is qualified to run at 125MHz. The CPU chip set does not support traditional
DRAMs.
The HP Integrity rx7620 Server supports DIMMs with densities of 64, 128, 256, and 512 Mb for
the SDRAM devices. Figure 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.
You must load DIMMs 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
Memory Component DensityTotal CapacityDIMM Size
64 megabit8 GB256 MB
128 megabit16 GB512 MB
256 megabit32 GB1 GB
512 megabit64 GB2 GB
1024 megabit128 GB4 GB
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 0.5 GB of main memory using
two 256 MB 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 2 GB DIMMs.
24 Introduction