HP rp7420, Service Manual, Page: 23 / 127

Figure 1-7 Memory Subsystem
PDH Riser Board
The Platform Dependant Hardware Riser board is a daughter card for the cell board. It contains
a micro-processor memory interface microcircuit, processor-dependent hardware including the
processor-dependent code (PDC), flash memory, and a manageability microcontroller, called
the Platform Dependant Hardware Controller (PDHC) with associated circuitry. The PDH obtains
cell board configuration information from cell board signals and from the LPM on the cell.
The PDH riser board contains circuitry that the cell board requires to function and, therefore,
each cell board must have a PDH riser installed before it is added to a server.
Central Processor Units
The cell board can hold up to eight (four dual-core) CPUs and can be populated with CPUs in
increments of two CPUs. On a cell board, the processors must be the same type and speed. Two
CPUs is the minimum configuration allowed on the HP 9000 rp7420 server. There are two
Frontside Buses (FBS), one for sockets 0 and 1, and one for sockets 2 and 3. Each FBS must have
either a CPU or a terminator at the end of the bus or the board does not operate properly. There
cannot be a terminator board in socket 1 or socket 3 locations. For the CPU load order that must
be maintained when adding CPUs to the cell board, see
Table 1-2 . For the locations on the cell
board for installing CPUs, see Figure 1-8 .
Table 1-2 Cell Board CPU Load Order
Socket 3 Location Socket 2 Location Socket 1 Location Socket 0 Location Number of
CPUs Installed
Empty Terminator Empty slot CPU installed Two
Empty CPU installed Empty slot CPU installed Four
Detailed HP 9000 rp7420 Server Description 23