Intel 64 and IA-32 Architectures Software Developers Manual Volume 3A, System Programming Guide, Part 1
13-14 Vol. 3A
POWER AND THERMAL MANAGEMENT
this bit or a reset. If bit 7 = 1, the Threshold #1 has been reached. Software may
clear this bit by writing a zero.
• Thermal Threshold #2 Status (bit 8, RO) — Indicates whether actual
temperature is currently higher than the value set in Thermal Threshold #2. If
bit 8 = 0, the actual temperature is lower. If bit 8 = 0, the actual temperature is
greater than or equal to TT#2.
• Thermal Threshold #2 Log (bit 9, R/WC0) — Sticky bit that indicates
whether the Thermal Threshold #2 has been reached since the last clearing of
this bit or a reset. If bit 9 = 1, the Thermal Threshold #2 has been reached.
Software may clear this bit by writing a zero.
• Digital Readout (bits 22:16, RO) — Digital temperature reading in 1 degree
Celsius relative to Tj(Max). 0 = Tj(Max); 1 = Tj(Max) - 1
o
C; etc. See the
processor’s data sheet for details regarding Tj(Max).
• Resolution in Degrees Celsius (bits 30:27, RO) — Specifies the resolution
(or tolerance) of the digital thermal sensor. The value is in degrees Celsius. It is
recommended that new threshold values be offset from the current temperature
by at least the resolution + 1 in order to avoid hysteresis of interrupt generation.
• Reading Valid (bit 31, RO) — Indicates if the digital readout in bits 22:16 is
valid. The readout is valid if bit 31 = 1.
Changes to temperature can be detected using two thresholds (see Figure 13-9); one
is set above and the other below the current temperature. These thresholds have the
capability of generating interrupts using the core's local APIC which software must
then service. Note that the local APIC entries used by these thresholds are also used
by the Intel® Thermal Monitor; it is up to software to determine the source of a
specific interrupt.
Figure 13-9. IA32_THERM_INTERRUPT Register
63
0
Reserved
15
Threshold #2 Interrupt Enable
12345814
16222324
Threshold #2 Value
Threshold #1 Interrupt Enable
Threshold #1 Value
Overheat Interrupt Enable
FORCPR# Interrupt Enable
THERMTRIP Interrupt Enable
Low Temp. Interrupt Enable
High Temp. Interrupt Enable