Datasheet

System Management Intel® S5000 Server Board Family Datasheet
Revision 1.3
Intel order number D38960-006
122
4.8.1 Servicing Events
Events can be received while the SEL is being cleared. The BMC implements an event
message queue to avoid the loss of messages. Queued messages are not overwritten.
The BMC recognizes duplicate event messages by comparing sequence numbers and the
message source. For more information, see the IPMI 2.0 Specification. Duplicate event
messages are discarded (filtered) by the BMC after they are read from the event message
queue. This means the queue can contain duplicate messages.
4.8.2 SEL Erasure
SEL erasure is a background process. SEL events that arrive during the erasure process will be
queued until the erasure is complete and then committed to the SEL.
SEL erasure generates an event logging disabled sensor event.
4.8.3 Timestamp Clock
The BMC maintains a four-byte internal timestamp clock used by the SEL and sensor data
record (SDR) sub-systems. This clock is incremented once per second.
4.8.3.1 Clock Initialization and Synchronization
If the BMC loses standby power, then when the power is restored, the BMC reads the real-time
clock (RTC) in the SIO chip and uses this value to update the BMC’s internal system clock. The
clock is used for SEL timestamps and programmed system wake-ups.
The actual system clock used by the BIOS and the operating system is based on a RTC in the
Intel
®
5000 Series Chipsets’ ICH component, not on the component in the SIO that the BMC
uses to initialize its clock. As a result, it is possible for synchronization issues to exist between
the BMC clock and the real-time clock. In some situations, the BIOS updates the BMC clock.
This alleviates possible mismatch problems as described below:
 System boot: At each system boot, the BIOS checks the BMC timestamp clock and only
updates this clock if the time is inaccurate. This reduces extra SEL entries.
 SMI handler: The BIOS programs the chipset to generate an SMI when the operating
system is shutting down (transition to S3, S4, or S5). This is necessary to download the
sleep state information to BMC. During this SMI, the BIOS will read the time from the
system RTC and then update BMC clock.
Whenever the BMC receives the Set SEL Time command, it updates the private RTC in the SIO
to match the system time. That helps ensure that the BMC RTC is in sync with system RTC.
If the system time (for instance, set through an operating system interface) is changed, the BMC
time clock will not be re-synchronized until the operating system shuts down the server, or, in
case of a non-graceful shutdown, when the server is rebooted.