JG82852GMSL7VP Datasheet, PDF (146/176 Pages) Intel Corporation – Intel® 852GM/852GMV Chipset Intel® 852GM/852GMV Chipset Hub (GMCH)

Power and Thermal Management
6.4.3.
R
Hysteresis Operation
Hysteresis provides a small amount of positive feedback to the thermal sensor circuit to prevent a trip
point from flipping back and forth rapidly when the temperature is right at the trip point.
6.5. External Thermal Sensor Input
An external thermal sensor with a serial interface may be placed next to DDR SDRAM SO-DIMM (or
any other appropriate platform location), or a remote Thermal Diode may be placed next to the SO-
DIMM (or any other appropriate platform location) and connected to the external Thermal sensor. Intel
advises that the external Thermal sensor contains some form of hysteresis, since none is provided by the
GMCH hardware.
The external sensor can be connected to the ICH4-M 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, which remains asserted for as long as the
Over-Temp Condition exists, and deasserts when temperature has returned to within normal operating
range. This external sensor output will be connected to the GMCH input (EXTTS_0) 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-ORed together allow
signaling from multiple sensors located physically separately. Software can, if necessary, distinguish
which SO-DIMM(s) is the source of the over-temp through the serial interface. However, since the SO-
DIMM(s) will be located on the same System Memory Bus Data lines, any GMCH-based Read Throttle
will apply equally.
Note: The use of external sensors that include an internal pull-up resistor on the open-drain thermal trip output
is discouraged. However, it may be possible depending on the size of the pull-up and the voltage of the
sensor. Please refer to the platform design guide for more information.
6.5.1.
Usage
External Sensor(s) Used for Dynamic Temperature Feedback Control in production releases:
Sensor on SO-DIMMs, which can be used to dynamically control read throttling.
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Intel^® 852GM/852GMV Chipset GMCH Datasheet