Guidelines

Thermal Specifications
16 Intel
®
7500 Chipset Thermal Mechanical Design Guide
TSTHRHI is used to determine throttling point as the temperature increases, and the
threshold TSFSC is an offset between the throttling point and the fan speed control
point. Threshold TSFSC value is 3. The Tcontrol of 92 °C is a conceptual threshold value
to be compared against the thermal sensor reading.
When TSFSC > 3, which means IOH thermal sensor reading is less than Tcontrol of
92 °C, system can run under acoustic condition.
When TSFSC <=3, which means IOH thermal sensor reading is larger than Tcontrol,
The fans must increase as necessary to try to maintain the TSFSC reading >=3. In the
cases where maximum fan speed is reached and TSFSC cannot be maintained at >=3,
the Tcase must still be maintained to be less than or equal to Tcase_max.
Note:
1. In addition to meeting the Tcase_max/Tcase_min specifications listed above, the
Intel
®
Itanium
®
processor 9300 series platform will need to support the system
fan speed control feature of the Intel
®
7500 chipset. This will be enabled by the
programming of the TSFSC, TSTHRHI, and TSTHRLO registers in the component.
The values in these registers will be used in conjunction with a temperature-
sensitive circuit on Intel 7500 chipset to dictate information to the BIOS for fan
speed control.
2. The reference Tall Heatsink is described in Chapter 6 and the reference Short
Heatsink is described in Chapter 7.
3. Tcontrol is a specific Tsensor reading which is programmed in the IOH MSR, BIOS
will obtain this data for fan speed control.
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