Thermal Diode Offset
A temperature offset value (specified as Toffset in
Pentium M Processor Model Specific Register (MSR). This offset is determined by using a thermal
diode ideality factor mean value of n = 1.0022 (shown in
be applied to the junction temperature read by the thermal diode. Any temperature adjustments due
to differences between the reference ideality value of 1.0022 and the default ideality values
programmed into the on-board thermal sensors, will have to be made before the above offset is
Table 5-2. Thermal Diode Interface
Table 5-3. Thermal Diode Specification
1. Intel does not support or recommend operation of the thermal diode under reverse bias. Intel does not
support or recommend operation of the thermal diode when the processor power supplies are not within their
specified tolerance range.
2. Characterized at 100 °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
and T = absolute temperature (Kelvin).
Value shown in the table is not the Pentium M Processor thermal diode ideality factor. It is a reference value
used to calculate the Pentium M Processor thermal diode temperature offset.
5. The series resistance, R
board trace resistance between the socket and the external remote diode thermal sensor. R
remote diode thermal sensors with automatic series resistance cancellation to calibrate out this error term.
Another application is that a temperature offset can be manually calculated and programmed into an offset
register in the remote diode thermal sensors as exemplified by the equation:
6. Offset value is programmed in processor Model Specific Register.
Forward Bias Current
Thermal diode temperature
Reference Diode Ideality
Factor used to calculate
= saturation current, q = electronic charge, V
, is provided to allow for a more accurate measurement of the diode junction
as defined includes the pins of the processor but does not include any socket resistance or
Thermal Specifications and Design Considerations
5-3) will be programmed into a
5-3) as a reference. This offset must
= voltage across the diode, k = Boltzmann Constant,
Thermal diode anode
Thermal diode cathode
Notes 2, 3, 4
2, 3, 5
can be used by