System Overview 1-15
! s1: Processor sleep state.
No context will be lost in this state and the processor caches will maintain
coherency.
! s4: Hibernate or Save to Disk.
The memory and machine state are saved to disk. Pressing the power button or
other wakeup event restores the system state from the disk and resumes normal
operation. This assumes that no hardware changes have been made to the system
while it was off.
! s5: Soft off.
Only the RTC section of the chipset and the BMC are running in this state.
System Board Management Controller (BMC)
Server management is concentrated in the System Board Management Controller
(BMC). The BMC and associated circuitry are powered from a 5Vdc standby voltage,
which remains active when system power is switched off, but the ac power source is
still on and connected.
The BMC supports the Management Workstation Application (MWA), which allows
remote server management via a modem or direct connection to a manager system.
Events monitored by the manager system include over-temperature and over-voltage
conditions, fan failure, or chassis intrusion.
Information on the Management Workstation Application (MWA) may be found in
Appendix B of this User’s Guide.
One major function of the BMC is to autonomously monitor system management
events, and log their occurrence in the nonvolatile System Event Log (SEL). The events
being monitored include overtemperature and overvoltage conditions, fan failure, or
chassis intrusion. To enable accurate monitoring, the BMC maintains the nonvolatile
Sensor Data Records (SDRs), from which sensor information can be retrieved. The
BMC provides an ISA host interface to SDR sensor information, so that software
running on the server can poll and retrieve the server's current status.
The BMC performs the following:
! Monitors server board temperature and voltage
! Monitors processor presence and controls Fault Resilient Boot (FRB)
! Detects and indicates baseboard fan failure
! Manages the SEL interface
! Manages the SDR Repository interface
! Monitors the SDR/SEL timestamp clock
! Monitors the system management watchdog timer
! Monitors the periodic SMI timer
! Monitors the event receiver