3XX Datasheet, PDF (67/82 Pages) Intel Corporation – Celeron D Processor

Thermal Specifications and Design Considerations
5.2.5
T_CONTROL and Fan Speed Reduction (Optional)
T_CONTROL and Fan Speed Reduction are not requirements for the Celeron D processor on 90 nm
process and in the 478-pin package, but are provided as options for platforms that can use these
features. T_CONTROL is part of the temperature specification that defines temperature for system fan
speed management. The BIOS reads the T_CONTROL value once and configures the fan control chip
appropriately. The value for T_CONTROL will be set during manufacturing and is unique for each
processor. The T_CONTROL temperature for a given processor can be obtained by reading the
IA32_TEMPERATURE_TARGET MSR in the processor and is in hexadecimal format.
The value of T_CONTROL (read from IA32_TEMPERATURE_TARGET MSR) can vary from 00 h
to 1E h (0 to 30 °C). The T_CONTROL read from the IA32_TEMPERATURE_TARGET MSR needs
to be added to a base value of 50 °C to get the final value for comparison with Thermal Diode
temperature (T_DIODE). T_CONTROL plus the base value of 50 °C is compared to the temperature
reported by T_DIODE. When the T_DIODE temperature is below T_CONTROL, fan speed can be at
minimum. As T_DIODE approaches T_CONTROL plus the base value of 50 °C, fan speed should be
increased in an effort to maintain T_DIODE at/below T_CONTROL plus the base value of 50 °C. For
platforms that support this feature, the processor T_C-MAX specification must be within guidelines,
as defined by the processor thermal specifications in Table 5-1. For 845G/x chipset platforms that
were not designed to read IA32_TEMPERATURE_TARGET MSR, the processor must be kept
within the T_C-MAX specification.
5.2.6 Thermal Diode
The processor incorporates an on-die thermal diode. A thermal sensor located on the system board
may monitor the die temperature of the processor for thermal management/long term die
temperature change purposes. Table 5-2 and Table 5-3 provide the diode parameter and interface
specifications. This thermal diode is separate from the Thermal Monitor’s thermal sensor and
cannot be used to predict the behavior of the Thermal Monitor.
Table 5-2. Thermal Diode Parameters
Symbol
Parameter
Min
Typ
Max
Unit
Notes
I_FW
Forward Bias Current
n
Diode Ideality Factor
11
—
187
uA
1
1.0083 1.011 1.0137 —
2,3,4
R_T
Series Resistance
3.242
3.33
3.594
Ω
2,3,5
NOTES:
1. Intel does not support or recommend operation of the thermal diode under reverse bias.
2. Characterized at 75 °C.
3. Not 100% tested. Specified by design characterization.
4. The ideality factor, n, represents the deviation from ideal diode behavior as exemplified by the diode equation:
I_FW = I_S * (e ^qVD/nkT –1)
where I_S = saturation current, q = electronic charge, V_D = voltage across the diode, k = Boltzmann Constant,
and T = absolute temperature (Kelvin).
5. The series resistance, R_T, is provided to allow for a more accurate measurement of the junction temperature. R_T, as defined,
includes the pins of the processor but does not include any socket resistance or board trace resistance between the socket
and the external remote diode thermal sensor. R_T can be used by remote diode thermal sensors with automatic series re-
sistance cancellation to calibrate out this error term. Another application is that a temperature offset can be manually calcu-
lated and programmed into an offset register in the remote diode thermal sensors as exemplified by the equation:
T_error = [R_T * (N-1) * I_FWmin] / [nk/q * ln N]
where T_error = sensor temperature error, N = sensor current ratio, k = Boltzmann Constant, q = electronic
charge.
Datasheet
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