Technical data

4-4 Using the System Controller
4.2.5 Initiating a System Power-Off
If a condition is detected that calls for a system shutdown, the System Controller issues an
alarm. If the situation is not immediately dangerous, the System Controller will wait until
it receives a “Set System Off” message or until its internal timer counts down. This delay
in the shutdown sequence is designed to give UNIX ample time to perform an orderly
software shutdown and to sync the system disks before power is removed.
If the reason for the shutdown requires immediate action, such as an out-of-spec voltage or
a voltage failure POK condition, the System Controller will log a message and shut down
immediately. In these cases, the power subsystem is shut down gracefully, but the system
does not have time to sync disks or to halt UNIX.
Following the alarm, the System Controller disables power to the system boards and
peripherals using the PENx_low signal without turning off the 48 volts from the OLSs. The
System Controller displays a fault message and the fault LED next to the status panel lights.
Note: First, check the status panel’s event history display for error messages. Then,
inspect the corresponding Fault LEDs to localize the problem. The appropriate
fault LEDs will remain lit after the system has shut down. Turning off the system
power (using either the key switch or the circuit breaker) or rebooting will reset the
fault LEDs only if the fault has been corrected.
Restore power by turning the key switch Off for 30 seconds, and then On (turning the key
switch Off clears any fault LEDs that are lit). The System Controller will begin the start-up
sequence. If the fault still exists, the system will shut down again and repeat the previous
fault message.
Caution: Overvoltage faults are potentially damaging to the system components. Refer
to the “Error Message” section for more information.
4.2.5.1 Overtemperature Faults
The System Controller monitors temperature sensors on the CPU (IP19 and IP21), MC3,
IO4, and 512S (rackmount systems only). Additionally, there is an inlet temperature sensor
located in the upper right corner of the cardcage in the deskside systems, and in either CC3
or on the jumper board in the rackmount systems.
If the System Controller shuts the system down because the temperature sensors on one or
more of the boards is too high, power is removed from all system components, including
the System Controller itself. To determine the origin of the fault, cycle the key switch off
and then on and check the displayed error message. If the system immediately shuts down
again, wait for several minutes to allow the mechanical temperature sensor switch to cool
below its trip point.