There are two types of power supplies: power/cooling modules (PCMs) and peripheral power supplies. PCMs provide DC current and cooling air to boards in the card cage. The peripheral power supply provides current for peripheral devices (such as a tape or CD-ROM drive) in the media tray.
The DC power to the centerplane is supplied by one or more PCMs. Each PCM also provides cooling air for two board slots. If a slot contains a board, the adjacent PCM slot must contain a PCM to supply cooling air.
Current from individual PCMs is shared on the centerplane.
With automatic system reconfiguration (ASR), a PCM can be taken offline and replaced without halting the system. There are two restrictions:
The remaining power/cooling modules must provide sufficient electrical power. As a general rule, the number of boards must be less than half the number of PCMs.
The PCM should be replaced quickly so that any adjacent boards will not overheat from lack of fan cooling.
A system has one peripheral power supply. This power supply provides DC power for the CD-ROM/tape tray and precharge power for hot-plugging boards and power/cooling modules. The +5 VDC output of the peripheral power supply is current shared with the +5 VDC outputs of the power/cooling modules.