American Megatrends MegaRAC M300V, Руководство пользователя

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Chapter Eight : Motherboard Hardware Support
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Motherboard Support for I/O Functions
The OPMA interface dedicates a fixed number of I/O signals to discrete sensors monitored by the
MegaRAC M300V card. These I/O signals are defined in the OPMA interface signal definition
section. If the motherboard requires additional discrete I/O sensors to be monitored for additional
manageability functions then those signals should be routed through I
2
C or SMBus-based GPIO
expanders. If any of these additional signals require interrupt attention from the MegaRAC
M300V card (as opposed to routine sensor polling performed by the MegaRAC M300V card) then
an I
2
C or SMBus-based GPIO expander with interrupting capability may be used to drive the
OPMA SYS_SMBUS_IO_EXP_INTR_L signal.
Example:
If the motherboard requires the MegaRAC M300V card to monitor a power supply
presence/absence condition, the OPMA connector does not have a dedicated pin for this sensor.
Accordingly, the motherboard must provide this signal through an I
2
C or SMBus-based GPIO
expander (such as an PCF 8575 device). Since this sensor does not require an interrupt attention
from the MegaRAC M300V card, an 8575 device would suffice in this case. When defining
manageability subsystem I/O requirements, the motherboard designer should carefully consider
which I
2
C or SMBus expander-based GPIO signals may or may not require interrupting
capabilities for manageability functions and then select the proper type of GPIO expander
accordingly.
Motherboard Support for MegaRAC M300V SCI Interrupt Signal
The motherboard must route the MCARD_SCI_INT_L signal from the OPMA connector to an
input on the Southbridge that is capable of generating an SCI (System Control Interrupt) to the
ACPI subsystem. The MegaRAC M300V card firmware will activate this output based on specific
conditions and policies that are defined for a particular system and the system level response to
this interrupt will be based on those preset policies. This interrupt is intended to allow the BMC to
initiate communications with the ACPI software running on the host system.
A typical usage would be as a replacement for certain types of temperature polling by server
software. Instead of requiring the system to poll the BMC for system temperatures, the BMC
would interrupt the ACPI subsystem when certain threshold temperatures were reached. OSPM at
the system level could then reduce the heat generation of the processor(s) and/or other BMC-
monitored devices.
Motherboard I/O Terminations
All motherboard hardware I/Os that interface with the OPMA connector must have 3.3-V input
buffers. Also, motherboard hardware requirements must be implemented with 3.3-V signal logic.