Figure 1-6 Cell Board
The server has a 48 V distributed power system and receives the 48 V power from the system
backplane board. The cell board contains DC-to-DC converters to generate the required voltage
rails. The DC-to-DC converters on the cell board do not provide N+1 redundancy.
The cell board contains the following major buses:
• Front side buses (FSB) for each of the four processors
• Four memory buses (one going to each memory quad)
• Incoming and outgoing I/O bus that goes off board to an SBA chip
• Incoming and outgoing crossbar busses that communicate to the crossbar chips on the system
backplane
• PDH bus that goes to the PDH and microcontroller circuitry
All of these buses come together at the CC chip.
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).
18 HP Integrity rx8640 and HP 9000 rp8440 Server Overview
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