System Overview 1-11Note: The system is Off only when the AC power cord is disconnected.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 isstill on and connected.The BMC supports the Management Workstation Application (MWA), which allowsremote server management via a modem or direct connection to a manager system.Events monitored by the manager system include over-temperature and over-voltageconditions, fan failure, or chassis intrusion.Information on the Management Workstation Application (MWA) may be found inAppendix B of this User’s Guide.One major function of the BMC is to autonomously monitor system managementevents, and log their occurrence in the nonvolatile System Event Log (SEL). The eventsbeing monitored include overtemperature and overvoltage conditions, fan failure, orchassis intrusion. To enable accurate monitoring, the BMC maintains the nonvolatileSensor Data Records (SDRs), from which sensor information can be retrieved. TheBMC provides an ISA host interface to SDR sensor information, so that softwarerunning 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! Controls secure mode, including video blanking, diskette write-protectmonitoring, and front panel lock/unlock initiation! Controls Wake On LAN via Magic Packet support.
