JG82875 S L8DB Intel, JG82875 S L8DB Datasheet - Page 140

• Manufacturer Part Number: JG82875 S L8DB
• Manufacturer: Intel

Specifications of JG82875 S L8DB

• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Compliant

Functional Description
5.5
5.5.1
140
Note: The use of external sensors that include an internal pull-up resistor on the open-drain thermal trip
Thermal Management
The MCH implements the following thermal management mechanisms. The mechanisms manage
the reads and writes cycles of the system memory interface, thus, ensuring that the temperature can
return to the normal operating range.
Hardware-based thermal management
The number of hexwords transferred over the DRAM interface are tracked per row. The tracking
mechanism takes into account that the DRAM devices consume different levels of power based on
cycle type (i.e., page hit/miss/empty). If the programmed threshold is exceeded during a
monitoring window, the activity on the DRAM interface is reduced. This helps in lowering the
power and temperature.
Software-based thermal management
This is used when the external thermal sensor in the system interrupts the processor to engage a
software routine for thermal management.
External Thermal Sensor Interface Overview
An external thermal sensor with a serial interface (e.g., the National Semiconductor LM77, LM87,
or other) may be placed next to DDR DIMM (or any other appropriate platform location), or a
remote thermal diode may be placed next to the DIMM (or any other appropriate platform location)
and connected to the external thermal sensor.
The external sensor can be connected to the ICH5 via the SMBus interface to allow programming
and setup by BIOS software over the serial interface. The external sensor’s output should include
an active-low open-drain signal indicating an over-temp condition (e.g., LM77 T_CRIT# or INT#
in comparator mode). The sensor’s output remains asserted for as long as the over-temp condition
exists and deasserts when the temperature has returned to within normal operating range. This
external sensor output will be connected to the MCH input (EXTTS#) and will trigger a preset
interrupt and/or read-throttle on a level-sensitive basis.
Additional external thermal sensor’s outputs, for multiple sensors, can be wire-OR’d together
allow signaling from multiple sensors located physically separately. Software can, if necessary,
distinguish which DIMM(s) is the source of the over-temp through the serial interface. However,
since the DIMMs will be located on the same memory bus data lines, any MCH-base read throttle
will apply equally.
output is discouraged; however, it may be possible depending on the size of the pull-up and the
voltage of the sensor.
Intel
®
82875P MCH Datasheet