Sun Microsystems Ultra 5, Service Manual

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Appendix C Functional Description C-35
C.5 Power
This section discusses the following topics:
■
Section C.5.1 “Onboard Voltage Regulator” on page C-35
■
Section C.5.2 “Power Supply Memory” on page C-35
C.5.1 Onboard Voltage Regulator
The onboard voltage regulator meets VRM8.1 specifications. The output of the
voltage regulator is programmed by the module. The module drives VID[3:0], which
asks the regulator to generate the correct core voltage for the CPU module core
voltage and SRAM IO.
C.5.2 Power Supply Memory
The system remembers the state that it was in before a power failure or accidental
power cord removal. This circuit is implemented on the motherboard. A latching
relay circuit on the motherboard performs this function.
C.5.3 Power Management
To meet EPA Energy Star requirements, the system power consumption is lower than
30 watts.
In-system software monitors system activity, and based on the system control
settings, system software saves the machine state (including the memory) onto the
hard drive and halts the operating system. The system software then turns off the
power supply.
Based on the setting of the NVRAM/TOD, which has an alarm clock, the system is
turned on automatically if the alarm is set. This is done by having the interrupt out
of the NVRAM/TOD directly connected to the power supply. The power supply
requires a
power_off
signal for the system software to be able to write to a bit
within a register and have the power supply shut down.