Platform Management
Intel® Server Board X38ML
Revision
1.3
Intel order number E15331-006
56
3. The BMC waits 10 seconds. If the power state retention feature is configured to power
on the server after an AC loss, it attempts to power up the server. This is the case when
either the AC dropped out momentarily, but not long enough to reset the BMC, or the
power subsystem had a momentary failure that the BMC could not differentiate from a
momentary AC loss.
The BMC responds to the power loss interrupt with 1 to 2 ms if it is in operational mode.
5.2.3
Power-up Sequence
To power up the server, the BMC simulates the front panel power button being pressed for 8
seconds or until
PS_PWRGD
is asserted. If
PS_PWRGD
is not asserted within 8 seconds, then
a fault is generated. See Section 5.17.3.
After simulating the front panel power button press, the BMC initializes all sensors to their
power-on initialization state. The initialization agent is run.
5.2.4
Power Down Sequence
To power down the system, the BMC simulates the front panel power button being pressed for 8
seconds or until
PS_PWRGD
is deasserted. If
PS_PWRGD
is not deasserted within 8 seconds,
then a fault is generated. See Section 5.17.3.
Before initiating the system power down, the BMC stops scanning any sensors that should not
be scanned in the powered-down state.
5.2.5
Power Control Sources
The following sources can initiate power-up and/or power-down activity:
Table 27. Power Control Initiators
Source
External Signal Name or
Internal Subsystem
Capabilities
Power button
Front panel power button
Turns power on or off
BMC watchdog timer
Internal BMC timer
Turns power off, or power cycle
Platform event filtering
PEF
Turns power off, power cycle, or reset
Command
Routed through command processor
Turns power on or off, or power cycle
Power state retention
Implemented via BMC internal logic
Turns power on when AC power returns
Chipset
Sleep S4/S5 signal (same as
POWER_ON
)
Turns power on or off
5.2.5.1
Power Button Signal
The
POWER_BUTTON
signal toggles the system power. This signal is activated by a
momentary contact switch on the front panel assembly and is routed to the BMC. The BMC de-
bounces and monitors the signal. The signal must be in a constant state for 8 ms before it is
treated as asserted.
