American Megatrends MegaRAC G4, User Manual

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Chapter Three : MegaRAC® G4 Card Layout 17
Power On Cable
(Runs between
the MegaRAC G4
and the Power On
Switch located
on Front Panel of
the Host System) Power On Cable
(Runs between the
MegaRAC G4 and the
Power On Header located
on the Host System’s
Motherboard)
Reset Switch Cable
(Runs between
the MegaRAC G4
and the Reset
Switch located
on Front Panel of
the Host System)
Reset Switch Cable
(Runs between
the MegaRAC G4
and the Reset
Header located
on the Host
System’s
Motherboard)
I2C Cable
(Optional, with Limitations.
Runs between the MegaRAC
G4 and the IPMB Header
located on the Host System’s
Motherboard)
MegaRAC Feature
Connector Cable
(Connects to J18)
IPMB (Intelligent Platform Management Bus)
The IPMI specification was developed by Intel, Dell, Hewlett-Packard, and NEC to
provide a standard interface to be used for monitoring server items such as temperature,
voltage, fans, power supplies, and chassis. IPMI is comprised of three specifications
Intelligent Platform Management Interface (IPMI), Intelligent Platform Management Bus
(IPMB) and Intelligent Chassis Management Bus (ICMB). The IPMI specification
defines the interface between management software and chassis management hardware.
The IPMB specification defines the internal Intelligent Platform Management Bus. The
ICMB specification defines an external bus for connecting additional IPMI enabled
systems.
The electrical interconnect for system management is based on the inter-IC (I2C) bus.
This bus is a two wire serial interface (clock, data) driven by open-collector drivers.
Devices arbitrate for the bus based on a collision detection mechanism. The I2C data and
I2C clock signals are referred to as an IPMB.
The IPMB connector can be used to read IPMI information from the motherboard's
System Management Controller. The format and definition of the IPMI information must
be based on the IPMI v1.5 Specification.
The IPMI specification was architected around the server motherboard environment. In a
typical motherboard, the Management Controller connects to a variety of dumb sensors
located on the motherboard and within the chassis. The command set contains commands
tailored to this environment and are intended to handle sensors, data repositories, event
logs and watchdog timers.