HP Integrity rx8640 Installation Manual page 23

Because of space limitations on the cell board, the PDH and microcontroller circuitry reside on a riser board
that plugs at a right angle into the cell board. The cell board also includes clock circuits, test circuits, and
decoupling capacitors.
PDH Riser Board
The server PDH riser board is a small card that plugs into the cell board at a right angle. The PDH riser
interface contains the following components:
• Microprocessor memory interface microcircuit
• Hardware including the processor dependant code (PDH) flash memory
• Manageability microcontroller with associated circuitry
The PDH obtains cell board configuration information from cell board signals and from the cell board local
power module (LPM).
Central Processor Units
The cell board can hold up to four CPU modules. Each CPU module can contain up to two CPU cores on a
single socket. Modules are populated in increments of one. On a cell board, the processor modules must be the
same family, type, and clock frequencies. Mixing of different processors on a cell or a partition is not
supported. See Table 1-1 on page 24 for the load order that must be maintained when adding processor
modules to the cell board. See Figure 1-7 on page 24 for the locations on the cell board for installing processor
modules.
Unlike previous HP cell based systems, the server cell board does not require that a
NOTE
termination module be installed at the end of an unused FSB. System firmware is allowed to
disable an unused FSB in the CC. This enables both sockets of the unused bus to remain
unpopulated.
Chapter 1
HP Integrity rx8640 and HP 9000 rp8440 Server Overview
Detailed Server Description
23