The power devices in a tall rack for the SGI Origin 3000 series servers shown in Figure 10-1 illustrate the following items:

The power devices on a short rack used to house the SGI Origin 3200 server (shown in Figure 10-2) include the following items:

The power bay's power management card, which connects to the power bay motherboard, is the control system for the power bay. The power management card, which provides a communication link between the power supplies and the power bay, contains the logic that powers on and powers off the power supplies and power bay ports, and monitors faults.

The power management card also contains a serial ID EEPROM that indicates the model and serial number of the unit and other information about the unit's capabilities and configuration. The L1 controller of a connecting brick reads this information via a serial bus (RS-422), which is part of the DC power cable.

Each power supply has three LEDs:

Table 10-1 lists conditions of the power supplies and the corresponding states of the LEDs.

Each power supply has two fans that move air from the front of the rack to the rear of the rack (see Figure 10-4). Blanking panels cover unoccupied spaces in the bay and must be present to prevent foreign objects from entering the power bay.

Each power bay contains either three or four distributed power supplies. The power bay supplies AC voltage to these power supplies and also monitors and controls the power supplies.

Each distributed power supply inputs the single-phase AC power can output 950 W at 48 VDC. The outputs are bussed together to provide a maximum of 3,800 W of available power in an N+1 redundant configuration, which means you have one additional 950 W power supply for reserve. This additional 950 W reserve power supply means that if you lose any one power supply, you still have enough power to power your system.

The number of power supplies in a power bay depends on the electrical requirements of the bricks in the rack. A minimum of two power supplies must be present per system at all times to provide standby 48 V power. A minimum of two supplies must be present to provide the N+1 redundant configuration. For example, a system with four C–bricks (which require a total of approximately 1232 W) and one R–brick (which requires approximately 60 W) would require three power supplies (two power supplies plus one redundant power supply, which together produce 2850 W).

The voltage regulator modules (VRMs) and DC-to-DC converters in each brick receive 48 VDC from the power bay and convert it to the voltage levels required by the brick components.

When the power bay receives power from the PDU or PDS and the 12 V enable for the brick is on, the power bay powers on the L1 controller by supplying a 12 V standby voltage to the brick. The L1 controller signals the power bay to supply the 48 VDC to its brick if the brick is enabled.

You can enable a brick by pressing the On/Off switch (brick reset button), located below the L1 display, or by entering a console command. The power bay does not supply the 48 VDC to the brick until the L1 controller signals it to do so. (Unlike the L1 controller, the L2 controller receives the 48 VDC from the power bay immediately.)

When the brick receives the 48 VDC, the L1 controller controls the application of the 48 VDC to the VRMs and DC-to-DC converters within the brick. The VRMs and DC-to-DC converters convert the 48 VDC to the voltage levels required by the brick components.