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82801AA and 82801AB Datasheet
5-63
Functional Description
The software can also directly read the status of the INTRUDER# signal (high or low) by clearing
and then reading the INTRD_DET bit. This allows the signal to be used as a GPI if the intruder
function is not required.
5.13.2.1
Handling an ECC Error or Other Memory Error
The host controller provides a message to indicate that it would like to cause an SMI#, SCI,
SERR#, or NMI. The software must check the host controller as to the exact cause of the error.
5.13.3
Alert on LAN* (ICH: 82801AA only)
ICH can interface directly with an Alert On LAN enabled LAN controller to report messages to a
network management console without the aid of the system processor. This is crucial in cases
where the processor is malfunctioning or cannot function due to being in a low-power state.
The basic scheme is for the ICH to send specific messages via the SMBus Interface to the LAN
controller. Upon receiving the SMBus message, the network controller has a prepared Ethernet
message that it can send to a network management console. The prepared message is typically
stored in a non-volatile memory connected directly to the network controller.
Messages are sent by the ICH over the SMBus either because a specific event has occurred or they
are sent periodically (also known as a heartbeat). The event and heartbeat messages have the exact
same format. The event messages are sent based on events occurring. The heartbeat messages are
sent every 30 to 32 seconds. When an event occurs, the ICH sends a new message and increments
the SEQ[3:0] field. For heartbeat messages the sequence number does not increment.
If the policy is for the ICH to reboot the system after a hardware lockup, the ICH will not send an
Alert On LAN message. Instead, the BIOS detects the lockup and sends the appropriate message.
If the policy is for the ICH not to reboot after a hardware lockup, the ICH sends an Alert On LAN
message with the Watchdog (WD) Event Status bit set. This message is sent as soon as the lockup
is detected. The message is sent with the next incremented sequence number. Until the locked
system is suspended (via a power button override) the ICH continues to send Alert On LAN
messages every heartbeat period (30-32 seconds). If another event occurs prior to a power button
override, the ICH sends another Alert On LAN message with the next incremented sequence
number and appropriate status bit set.
If a boot is unsuccessful (processor does not fetch the first instruction), the ICH sends an Alert On
LAN message with the processor event status bit set and the next incremented sequence number.
This message is sent as soon as the lockup is detected (2 TCO timer timeouts).