U.S. patent application number 10/464482 was filed with the patent office on 2003-11-13 for method and apparatus for programmable thermal sensor for an integrated circuit.
This patent application is currently assigned to Intel Corporation. Invention is credited to Pippin, Jack D..
Application Number | 20030212474 10/464482 |
Document ID | / |
Family ID | 22417696 |
Filed Date | 2003-11-13 |
United States Patent
Application |
20030212474 |
Kind Code |
A1 |
Pippin, Jack D. |
November 13, 2003 |
Method and apparatus for programmable thermal sensor for an
integrated circuit
Abstract
A programmable thermal sensor is implemented in an integrated
circuit such as a microprocessor. The programmable thermal sensor
monitors the temperature of the integrated circuit, and generates
an output to indicate that the temperature of the integrated
circuit has attained a pre-programmed threshold temperature. In a
microprocessor implementation, the microprocessor contains a
processor unit, an internal register, microprogram and clock
circuitry. The microprogram writes programmable input values,
corresponding to threshold temperatures, to the internal register.
The programmable thermal sensor reads the programmable input
values, and generates an interrupt when the temperature of the
microprocessor reaches the threshold temperature. In addition to a
programmable thermal sensor, the microprocessor contains a fail
safe thermal sensor that halts operation of the microprocessor when
the temperature attains a critical temperature.
Inventors: |
Pippin, Jack D.; (Portland,
OR) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Intel Corporation
Santa Clara
CA
|
Family ID: |
22417696 |
Appl. No.: |
10/464482 |
Filed: |
June 19, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10464482 |
Jun 19, 2003 |
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08636024 |
Apr 19, 1996 |
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08636024 |
Apr 19, 1996 |
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08401473 |
Mar 9, 1995 |
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08401473 |
Mar 9, 1995 |
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08124980 |
Sep 21, 1993 |
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Current U.S.
Class: |
700/300 ;
714/E11.018 |
Current CPC
Class: |
G05F 3/265 20130101;
G05D 23/19 20130101; G06F 11/3058 20130101; G06F 11/3093 20130101;
G05F 3/267 20130101; Y02D 10/00 20180101; G06F 1/206 20130101; G06F
11/3024 20130101; G06F 1/324 20130101 |
Class at
Publication: |
700/300 |
International
Class: |
G05D 023/00 |
Claims
What is claimed is:
1. A computer, comprising: a clock module, said clock module
produces a clock signal having two or more different frequencies; a
processor operatively connected to said clock module, said
processor processes instructions in accordance with the clock
signal; a temperature sensor operatively connected to said clock
module, said temperature sensor produces a temperature signal based
on the temperature of said processor; a fan; a fan controller, said
fan controller activates the fan in response to the temperature
signal, wherein the frequency of the clock signal supplied to said
processor varies depending on the temperature of said
processor.
2. A computer as recited in claim 1, wherein the frequency of the
clock signal supplied to said processor is reduced as needed to
avert overheating of said processor.
3. A method for producing a clock signal for a microprocessor, said
method comprising: (a) providing a fast clock signal; (b) providing
a slow clock signal; (c) receiving a control signal related to the
temperature of the microprocessor; and (d) selecting between the
fast clock signal and slow clock signal in accordance with the
control signal, wherein the control signal is influenced by
activity of a fan associated with the microprocessor.
4. A method as recited in claim 3, wherein the fast clock signal is
reduced to the slow clock signal by buffering, clock distribution,
or phase tuning.
5. A method for producing a clock for a microprocessor, said method
comprising: (a) producing a clock signal having a frequency which
varies in accordance with the chip temperature; and (b) supplying
the clock signal to the microprocessor, wherein the frequency of
the clock signal is influenced by activity of a fan associated with
the microprocessor which serves as an indicator of the chip
temperature.
6. A method as recited in claim 5, wherein said producing (a)
comprises: (a1) receiving a high frequency clock; and (a2) reducing
the high frequency clock to a slow frequency clock by buffering,
clock distribution, or phase tuning to avert overheating by said
processor.
7. A method for activating speed of a fan that cools a
microprocessor, said method comprising the operations of:
monitoring temperature of the microprocessor; producing a control
signal based on the temperature of the microprocessor; and
activating the fan in response to the control signal.
8. A method as recited in claim 7, wherein the fan and the
microprocessor are parts of a computer.
9. A computer system, comprising: a processor module, said
processor module processes instructions in accordance with a clock
signal, and said processor module supports a normal clock mode and
a plurality of reduced power modes; and a temperature sensor
thermally coupled to said processor module, said temperature sensor
produces a temperature signal based on the temperature of said
processor module, wherein the temperature signal from said
temperature sensor is used to regulate the temperature of said
processor module by altering the frequency of the clock signal, and
wherein overheating of said processor module is averted by reducing
the frequency of the clock signal to a value associated with one of
the reduced power modes.
10. A computer system as recited in claim 9, wherein said
temperature sensor is internal to said processor module.
11. A thermal management method for a computer system having a
microprocessor, the microprocessor performing operations at a rate
determined by a clocking frequency, said thermal management method
comprising the acts of: monitoring the temperature of the
microprocessor; comparing the temperature of the microprocessor to
first and second temperature thresholds, the second temperature
threshold being greater than the first temperature threshold;
reducing the clocking frequency when the temperature of the
microprocessor is greater than the first temperature threshold; and
reducing the clocking frequency a second time when the temperature
of the microprocessor exceeds the second temperature threshold.
12. A method as recited in claim 11, wherein the clocking frequency
is reduced a second time only after the reduction in the clocking
frequency does not operate to control thermal conditions of the
microprocessor.
13. A method as recited in claim 11, wherein said reducing the
clocking frequency is performed by one of buffering, clock
distribution, or phase tuning, and wherein said reducing the clock
frequency further reduces the clocking frequency when a prior
reduction in the clocking frequency is not able to prevent the
temperature of the microprocessor from continuing to increase.
14. A computer system, comprising: a microprocessor, said
microprocessor operating to perform operations in accordance with a
clocking frequency; a fan; a temperature sensor thermally coupled
to said microprocessor, said temperature sensor provides a
temperature indication corresponding to the temperature of said
microprocessor; and a thermal manager operatively connected to said
microprocessor and said fan, said thermal manager being configured
to receive the temperature indication from said temperature sensor,
and said thermal manager compares the temperature indication to
first and second temperature thresholds, causes the clocking
frequency for said microprocessor to be reduced a first time to
provide thermal management when the temperature indication
indicates that the temperature of said microprocessor exceeds the
first temperature threshold, activates said fan when the
temperature indication indicates that the temperature of said
microprocessor exceeds the first temperature threshold, and causes
the clocking frequency to be reduced a second time when the
temperature of the microprocessor exceeds the second temperature
threshold the second temperature threshold being greater than the
first temperature threshold.
15. A computer system as recited in claim 14, wherein said
temperature sensor is integrated into said microprocessor.
16. A computer system as recited in claim 14, wherein said second
reduction in clock frequency is used only after the first reduction
in the clocking frequency for said microprocessor does not operate
to sufficiently limit the temperature of said microprocessor.
17. A computer system as recited in claim 14, wherein when the
temperature indication indicates that the temperature of said
microprocessor does not exceed the second temperature threshold,
said second reduction in clock frequency is not implemented.
18. A computer system as recited in claim 14, wherein a plurality
of respectively lower clocking frequencies can be used to attempt
to stabilize the thermal conditions.
19. A computer system, comprising: a microprocessor, said
microprocessor operates in accordance with a clock signal having a
controllable frequency a fan; and a thermal management controller
operatively connected to said microprocessor and said fan, said
thermal management controller operates to thermally manage said
microprocessor in accordance with a first cooling mode and a second
cooling mode, the first cooling mode involving use of said fan for
cooling said microprocessor, and the second cooling mode involving
reduction in the controllable frequency of the clock signal for
cooling said microprocessor, wherein, with the first cooling mode,
said thermal management controller causes said fan to activate to
provide thermal cooling.
20. A computer system as recited in claim 19, wherein, with the
second cooling mode, said thermal management controller causes the
controllable frequency of the clock to be successively reduced as
needed to provided additional cooling.
21. A computer, comprising: a microprocessor that operates in
accordance with a clock, the clock having a controllable frequency;
a temperature sensor that measures a temperature; a fan; and a
thermal controller for providing thermal management of said
computer, said thermal controller has a first cooling mode and a
second cooling mode, the controllable frequency of the clock is
reduced to regulate thermal conditions when in the first cooling
mode, and said fan is activated to regulate thermal conditions when
in the second cooling mode, wherein when said thermal controller
operates in the first cooling mode, the controlled frequency of the
clock is reduced when the temperature exceeds a first temperature
threshold, and wherein when said thermal controller operates in the
second cooling mode, said fan is activated when the temperature
exceeds the first temperature threshold.
22. A computer as recited in claim 21, wherein said temperature
sensor measures the temperature of said microprocessor.
23. A computer as recited in claim 21, wherein said temperature
sensor is integral with said microprocessor.
24. A computer as recited in claim 21, wherein when said thermal
controller operates in the first cooling mode, the controllable
frequency of the clock is gradually and successively stepwise
reduced as needed to regulate thermal conditions.
25. A computer as recited in claim 21, wherein in the first cooling
mode cooling of said microprocessor is achieved primarily through
reduction in clock frequency for said microprocessor, and wherein
in the second cooling mode cooling said microprocessor is achieved
primarily through use of said fan.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to thermal sensing, and more
specifically to methods and apparatus for a programmable thermal
sensor in an integrated circuit.
[0003] 2. Art Background
[0004] Advances in silicon process technology has lead to the
development of increasingly larger die sizes for integrated
circuits. The large dies sizes permit integration of millions of
transistors on a single die. As die sizes for integrated circuits
become larger, the integrated circuits consume more power. In
addition, advances in microprocessor computing require execution of
a large number of instructions per second. To execute more
instructions per second, the microprocessor circuits operate at an
increased clock frequency. Therefore, a microprocessor containing
over one million transistors may consume over 30 watts of power.
With large amounts of power being dissipated, cooling becomes a
problem.
[0005] Typically, integrated circuits and printed circuit boards
are cooled by either active or passive cooling devices. A passive
cooling device, such as a heat sink mounted onto an integrated
circuit, has a limited capacity to dissipate heat. An active
cooling device, such as a fan, is used to dissipate larger amounts
of heat. Although a fan cooling system dissipates heat, there are
several disadvantages associated with such a system. Traditionally,
fans cool integrated circuits by air convection circulated by a
fan. However, when a fan is used in conjunction with a high density
multi-chip computer system, a large volume of air is required for
cooling thereby necessitating powerful blowers and large ducts. The
powerful blowers and large ducts implemented in the computer occupy
precious space and are too noisy. The removal of a cover or other
casing may result in a disturbance of air flow causing the fan
cooling system to fail. In addition, the fan cooling system is made
up of mechanical parts that have a mean time between failure (MTBF)
specification less than a typical integrated circuit. Furthermore,
fan cooling systems introduce noise and vibration into the
system.
[0006] In addition to cooling systems, thermal sensors are
implemented to track the temperature of an integrated circuit or
electronic system. Typically, thermal sensors consist of a thermal
couple which is directly attached to a heat sink. In more
sophisticated thermal sensing systems, a diode and external analog
circuitry are used. In operation, the voltage/current
characteristics of the diode change depending upon temperature of
the integrated circuit, and the external analog circuitry measures
the voltage or current characteristics of the diode. The additional
analog circuitry is complex and difficult to implement. In
addition, employing the analog circuitry results in a thermal time
delay degrading the accuracy of such a configuration. Moreover,
external analog circuitry for sensing the voltage of the diode
consumes a larger area than the integrated circuit being sensed.
Therefore, it is desirable to provide a thermal sensor which is
incorporated into the integrated circuit. In addition, it is
desirable to provide a thermal sensor that can provide feedback for
an active cooling system. Furthermore, it is desirable to control
the temperature of an integrated circuit without the use of a fan.
The present invention provides an integrated thermal sensor that
detects a threshold temperature so that active cooling of the
integrated circuit is accomplished through system control.
SUMMARY OF THE INVENTION
[0007] A programmable thermal sensor is implemented in an
integrated circuit. The programmable thermal sensor monitors the
temperature of the integrated circuit, and generates an output to
indicate that the temperature of the integrated circuit has
attained a predetermined threshold temperature. The programmable
thermal sensor contains a voltage reference, a programmable
V.sub.be, a current source, and a sense amplifier or comparator.
The current source generates a constant current to power the
voltage reference and the programmable V.sub.be. With a constant
current source, the voltage reference generates a constant voltage
over varying temperatures and power supply voltages. In a preferred
embodiment, the voltage reference is generated with a silicon
bandgap reference circuit. The constant voltage from the voltage
reference is one input to the sense amplifier. The programmable
V.sub.be contains a sensing portion and a multiplier portion. In
general, the programmable V.sub.be generates a voltage dependent
upon the temperature of the integrated circuit and the value of
programmable inputs. The programmable inputs are supplied to the
multiplier portion to generate a multiplier value for use in the
multiplier portion. The voltage reference is compared with the
voltage generated by the programmable V.sub.be in the sense
amplifier. The sense amplifier generates a greater than, less than
signal.
[0008] The programmable thermal sensor of the present invention is
implemented in a microprocessor. In addition to the programmable
thermal sensor, the microprocessor contains a processor unit, an
internal register, microprogram and clock circuitry. The processor
unit incorporates the functionality of any microprocessor circuit.
The clock circuitry generates a system clock for operation of the
microprocessor. In general, the microprogram writes programmable
input values to the internal register. The programmable input
values correspond to threshold temperatures. The programmable
thermal sensor reads the programmable input values, and generates
an interrupt when the temperature of the microprocessor reaches the
threshold temperature. In a first embodiment, the interrupt is
input to the microprogram and the processor unit. In response to an
interrupt, the processor unit may take steps to cool the
temperature of the microprocessor, and the microprogram programs a
new threshold temperature. For example, the processor may turn on a
fan or reduce the clock frequency. The new threshold temperature is
slightly higher than the current threshold temperature so that the
processor unit may further monitor the temperature of the
microprocessor.
[0009] In a second embodiment of the present invention, the
interrupt generated by the programmable thermal sensor is input to
external sensor logic. The external sensor logic automatically
controls the frequency of the microprocessor. If the temperature of
the microprocessor raises, then the clock frequency is decreased.
Conversely, if the temperature of the microprocessor drops, then
the system clock frequency is increased. In addition to a
programmable thermal sensor, the microprocessor contains a fail
safe thermal sensor. The fail safe thermal sensor generates an
interrupt when detecting that the microprocessor reaches a
pre-determined threshold temperature, and subsequently halts
operation of the system clock. The pre-determined threshold
temperature is selected below a temperature that causes physical
damage to the device. The microprocessor of the present invention
is implemented in a computer system. Upon generation of an
interrupt in the programmable thermal sensor, a message containing
thermal sensing information is generated and displayed to a user of
the computer system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The objects, features, and advantages of the present
invention will be apparent from the following detailed description
of the preferred embodiment of the invention with references to the
following drawings.
[0011] FIG. 1 illustrates a block diagram of a programmable thermal
sensor configured in accordance with the present invention.
[0012] FIG. 2 illustrates a graph depicting the relationship
between the base-emitter voltage (V.sub.be) of a bipolar transistor
versus temperature of the supply voltage.
[0013] FIG. 3 illustrates a bandgap reference circuit configured in
accordance with the present invention.
[0014] FIG. 4 illustrates a programmable base to emitter voltage
(V.sub.be) circuit configured in accordance with the present
invention.
[0015] FIG. 5 illustrates a current source, including the bandgap
reference circuit, configured in accordance with the present
invention.
[0016] FIG. 6 illustrates a sense amplifier for the thermal sensor
configured in accordance with the present invention.
[0017] FIG. 7 illustrates block diagram of a first embodiment of a
microprocessor incorporating a programmable thermal sensor
configured in accordance with the present invention.
[0018] FIG. 8 illustrates a flow diagram for a method of
controlling the programmable thermal sensor configured in
accordance with the present invention.
[0019] FIG. 9 illustrates a block diagram of a second embodiment of
a microprocessor incorporating a programmable thermal sensor
configured in accordance with the present invention.
[0020] FIG. 10 illustrates a block diagram of a microprocessor
incorporating a fail safe thermal sensor configured in accordance
with the present invention.
[0021] FIG. 11 illustrates a computer system incorporating a
microprocessor comprising thermal sensing configured in accordance
with the present invention.
NOTION AND NOMENCLATURE
[0022] The detailed descriptions which follow are presented, in
part, terms of algorithms and symbolic representations of
operations within a computer system. These algorithmic descriptions
and representations are the means used by those skilled in the data
processing arts to most effectively convey the substance of their
work to others skilled in the art.
[0023] An algorithm is here, and generally, conceived to be a
self-consistent sequence of steps leading to a desired result.
These steps are those requiring physical manipulations of physical
quantities. Usually, though not necessarily, these quantities take
the form of electrical or magnetic signals capable of being stored,
transferred, combined, compared, and otherwise manipulated. It
proves convenient at times, principally for reasons of common
usage, to refer to these signals as bits, values, elements,
symbols, characters, terms, numbers, or the like. It should be
borne in mind, however, that all of these and similar terms are to
be associated with the appropriate physical quantities and are
merely convenient labels applied to these quantities.
[0024] Further, the manipulations performed are often referred to
in terms, such as adding or comparing, which are commonly
associated with mental operations performed by a human operator. No
such capability of a human operator is necessary, or desirable in
most cases, in any of the operations described herein which form
part of the present invention; the operations are machine
operations. Useful machines for performing the operations of the
present invention include general purpose digital computers or
other similar devices. In all cases there should be borne in mind
the distinction between the method operations in operating a
computer and the method of computation itself. The present
invention relates to method steps for operating a computer in
processing electrical or other (e.g., mechanical, chemical)
physical signals to generate other desired physical signals.
[0025] The present invention also relates to apparatus for
performing these operations. This apparatus may be specially
constructed for the required purposes or it may comprise a general
purpose computer as selectively activated or reconfigured by a
computer program stored in the computer. The algorithms presented
herein are not inherently related to a particular computer or other
apparatus. In particular, various general purpose machines may be
used with programs written in accordance with the teachings herein,
or it may prove more convenient to construct more specialized
apparatus to perform the required method steps. The required
structure for a variety of these machines will appear from the
description given below. Machines which may perform the functions
of the present invention include those manufactured by Intel.RTM.
Corporation, as well as other manufacturers of computer
systems.
DETAILED DESCRIPTION
[0026] Methods and apparatus for thermal sensing in an integrated
circuit are disclosed. In the following description, for purposes
of explanation, specific nomenclature is set forth to provide a
thorough understanding of the present invention. However, it will
be apparent to one skilled in the art that these specific details
are not required to practice the present invention. In other
instances, well known circuits and devices are shown in block
diagram form to avoid obscuring the present invention
unnecessarily.
[0027] Referring to FIG. 1, a block diagram of a programmable
thermal sensor configured in accordance with the present invention
is illustrated. In general, a programmable thermal sensor 100
monitors the temperature of an integrated circuit, and generates an
output to indicate that the temperature of the integrated circuit
has attained a predetermined threshold temperature. The
programmable thermal sensor 100 contains a voltage reference 120, a
programmable V.sub.be 110, a current source 140, and a sense
amplifier 160. The current source 140 generates a constant current
to power the voltage reference 120 and the programmable V.sub.be
110. With a constant current source, the voltage reference 120
generates a constant voltage over varying temperatures and power
supply voltages (V.sub.cc). In a preferred embodiment, the voltage
reference is generated with a silicon bandgap reference circuit.
The constant voltage from the voltage reference 120 is input to the
sense amplifier 160. The programmable V.sub.be 110 contains a
sensing portion and a multiplier portion. In general, the
programmable V.sub.be 110 generates a voltage dependent upon the
temperature of the integrated circuit and the value of programmable
inputs. The programmable inputs are supplied to the multiplier
portion to generate a multiplier value for use in the multiplier
portion.
[0028] Referring to FIG. 2, a graph depicting the relationship
between the base-emitter voltage (V.sub.be) of a bipolar transistor
versus temperature is illustrated. A characteristic curve 200 on
the graph of FIG. 2 shows the linear characteristics of the
V.sub.be voltage over a temperature range of 70 degrees Fahrenheit
(70.degree. F.) to 140.degree. F. In addition, the graph of FIG. 2
shows a relative constant bandgap voltage curve 205 over the
specified temperature range. Although the bandgap voltage varies
slightly over the temperature range, the variation of the bandgap
voltage is negligible compared to the variation of the V.sub.be
voltage over the temperature range. As shown by the curve 205 in
FIG. 2, the bandgap voltage is equal to approximately 1.3 volts
(V). When the V.sub.be voltage equals 1.3 volts, the temperature of
the integrated circuit is 100.degree. F. Based on the linear
temperature characteristics of the V.sub.be voltage, and the
relatively constant bandgap voltage over the temperature range, a
thermal sensor is constructed.
[0029] For the voltage/temperature characteristics of line 200
shown in FIG. 2, the bandgap voltage equals the V.sub.be voltage
when integrated circuit is at 100.degree. F. However, the V.sub.be
voltage may be changed to sense additional temperature values in
the integrated circuit. By shifting the linear V.sub.be
voltage/temperature characteristic curve 200, any number of
predetermined thresholds temperature values are detected. To shift
the voltage/temperature characteristic curve 200, the V.sub.be
voltage is multiplied by predetermined values to generate a new
voltage for comparison to the bandgap voltage. Specifically, to
shift the characteristic curve 200 to sense a voltage less then
100.degree. F., the V.sub.be voltage is multiplied by a fraction to
generate a new characteristic curve, such as the characteristic
curve 210 shown in FIG. 2. The characteristic curve 210 exhibits
the same slope as the original characteristic curve 200. However,
for the characteristic curve 210, the V.sub.be voltage is equal to
the bandgap voltage when the integrated circuit temperature equals
90.degree. F. Similarly, the V.sub.be voltage may be multiplied by
a value greater than 1 to generate a characteristic curve such as
the characteristic curve 220 shown in FIG. 2. The characteristic
curve 220 also exhibits the same slope as the original
characteristic curve 200. However, the characteristic curve 220
intersects the bandgap voltage curve 205 at 120.degree. F.
Consequently, a any number of threshold temperatures are detectable
by multiplying the V.sub.be voltage by a predetermined
constant.
[0030] Referring to FIG. 3, a bandgap reference circuit configured
in accordance with the present invention is illustrated. The
bandgap reference circuit 120 is powered from a voltage source,
V.sub.cc. The voltage source V.sub.cc is regulated by a current
source such that the current source 140 supplies a constant current
over a wide range of V.sub.cc voltages. A preferred embodiment of
the present invention for the current source 140 is described fully
below. The bandgap reference circuit 120 contains three N-P-N
bipolar transistors Q1, Q2 and Q3, and three resistive elements R1,
R2 and R3. In general, the constant bandgap reference voltage,
V.sub.bandgap, is generated at the collector of N-P-N transistor
Q3. The bipolar transistors Q1, Q2 and resistive elements R1, R2
and R3 are provided to compensate for temperature variations in the
base to emitter junction voltage (V.sub.be) of bipolar transistor
Q3. Specifically, the resistive element R1 is coupled from the
current source 140 to the collector of bipolar transistor Q1. The
collector and base of bipolar transistor Q1 are shorted so that Q1
is effectively a P-N junction diode. The base of transistor Q1 and
the base of transistor Q2 are coupled together. The resistive
element R3 couples the collector of transistor Q2 to the current
source 140, and the resistive element R2 couples the emitter of
transistor Q2 to ground. In a preferred embodiment of the present
invention, the resistive element R1 equals 4800 ohms, the resistive
element R2 equals 560 ohms, and the resistive element R3 equals
4800 ohms.
[0031] In operation, the voltage at the base of transistors Q1 and
Q2 are pulled to the V.sub.bandgap voltage through the R1
resistance. Therefore, the transistors Q1 and Q2 are biased in the
active region, thereby allowing current to flow from the collector
to the emitter of transistors Q1 and Q2. The mirrored configuration
of transistors Q1 and Q2 tends to drive the base to emitter voltage
(V.sub.be) of transistors Q1 and Q2 equivalent. However, the
resistive element R2 increases the resistance at the emitter of
transistor Q2, resulting in a greater current density flowing
through transistor Q1 than flowing through transistor Q2. As the
temperature in the integrated circuit rises, the V.sub.be of
transistor Q2 decreases. In turn, the decrease of V.sub.be on
transistor Q2 causes a decrease in the current density flow through
Q2. The decrease in current density through the resistive element
R2 also causes a reduction in the current density flowing through
the resistive element R3. Because the collector of transistor Q2 is
coupled to the base of transistor Q3, a decrease in the current
through resistive element R3 results in an increase in the voltage
at the base of transistor Q3. Consequently, as the temperature of
the integrated circuit rises, the V.sub.be across transistors Q1,
Q2, and Q3 decreases. However, the decrease of V.sub.be on
transistor Q3 is compensated by the increase of voltage at the base
of transistor Q3. Therefore, regardless of temperature
fluctuations, the V.sub.bandgap remains at a constant silicon
bandgap voltage. For a further explanation of generation of a
bandgap reference, including a theoretical derivation, see A. T.
Brokaw, A Simple Three-Terminal IC Bandgap Reference, IEEE J. of
Solid State Circuits, December, 1974, and Karel E. Kuijk, A
Precision Reference Voltage Source, IEEE J. of Solid State
Circuits, June 1973.
[0032] Referring to FIG. 4, a programmable base to emitter voltage
(V.sub.be) circuit configured in accordance with the present
invention is illustrated. In a preferred embodiment of the present
invention, a temperature varying voltage is generated from the
characteristics of a base to emitter junction on a bipolar
transistor. In general, the programmable V.sub.be circuit generates
an output voltage, V.sub.out, based on the V.sub.be voltage and the
value of programmable input voltages Vp1, Vp2 and Vp3. A N-P-N
bipolar transistor Q11 shown in FIG. 4 is utilized to generate the
V.sub.be reference voltage. As described above, the
V.sub.be/temperature characteristic curve may be shifted along the
temperature axis to detect a desired threshold temperature. By
shifting the V.sub.be/temperature characteristic curve along the
temperature axis, a plurality of output voltages representing
different threshold temperatures are generated.
[0033] To generate the V.sub.out for a particular threshold
temperature, a programmable V.sub.be multiplier circuit is
utilized. The programmable V.sub.be multiplier circuit contains
resistive elements R5, R6, R7, R8, and R9, and metal oxide
semiconductor field effect transistors. (MOSFET) Q12, Q13, and Q14.
In a preferred embodiment, Q12, Q13 and Q14 comprise N-MOS
transistors. The drain terminal of transistor Q12 is coupled to a
first input on resistive element R7, and the source of transistor
Q12 is coupled to a second input on resistive element R7. The
transistors Q13 and Q14 are similarly coupled to resistive elements
R8 and R9, respectively. Programmable input voltages Vp1, Vp2, and
Vp3 are input to the gate of transistors Q12, Q13 and Q14,
respectively. The input voltages Vp1, Vp2, and Vp3 control the
current flow by selecting either a resistive element or the
respective MOS transistor.
[0034] In operation, the programmable V.sub.be multiplier circuit
outputs a voltage, V.sub.out, comprising a multiple of the base to
emitter voltage on bipolar transistor Q11. For purposes of
explanation, consider resistive elements R6, R7, R8 and R9 as one
resistive element: R6-R9. The resistive element R6-R9 is connected
across the base to emitter junction of bipolar transistor Q11.
Therefore, the voltage drop across the resistive element R6-R9 is
equivalent to V.sub.be of bipolar transistor Q11. The current
flowing through resistive element R6-R9 is approximately equal to
the current flowing through resistive element R5 minus the current
flowing into the base of transistor Q11. Therefore, if the value of
resistive element R5 is equal to the value of resistive element
R6-R9, the voltage at the collector of transistor Q11 equals
2V.sub.be. In general, the V.sub.out voltage is defined by the
following equation:
V.sub.out=V.sub.R5+V.sub.be
V.sub.be=V.sub.R6-R9
V.sub.out=V.sub.R5+V.sub.R6-R9
[0035] Therefore, V.sub.out values greater than 1V.sub.be are
generated by changing the ratio between resistive element R5 and
resistive element R6-R9.
[0036] To move the V.sub.be curve 200 shown in FIG. 2 along the
temperature axis via the programmable V.sub.be circuit 110, a
combination of resistive elements R7, R8 and R9 are selected. To
select a combination of resistive elements R7, R8 and R9, the
voltages Vp1, Vp2, and Vp3 are applied to the gates of MOS
transistors Q13, Q12, and Q14, respectively. The resistive elements
R7, R8 and R9 are binary weighed resistors. Each individual
resistor R7, R8 and R9 can be shorted through control by Q12, Q13
and Q14 respectively. By selecting resistive elements R7, R8 and R9
as series resistors with resistive element R6, the voltage
V.sub.out is changed. In a preferred embodiment of the present
invention, the resistive element R5 equals 6380, the resistive
element R6 equals 5880, the resistive element R7 equals 392, the
resistive element R8 equals 787, and the resistive element R9
equals 1568. By setting the resistive elements R5-R9 to the above
values and programming the transistors Q13, Q12, and Q14, the
voltage V.sub.out is generated to correspond to specific threshold
temperatures. Specifically, Table 1 illustrates the threshold
temperatures programmed in response to the input voltages Vp1, Vp2,
and Vp3.
1TABLE 1 Threshold Temperature Vp1 Vp2 Vp3 (Degrees C.) 0 0 0
70.degree. 0 0 1 80.degree. 0 1 0 90.degree. 0 1 1 100.degree. 1 0
0 110.degree. 1 0 1 120.degree. 1 1 0 130.degree. 1 1 1
140.degree.
[0037] Referring to FIG. 5, a current source including the bandgap
reference circuit configured in accordance with the present
invention is illustrated. The bandgap reference circuit comprises
resistors R1, R2, and R3 and bipolar transistors Q1, Q2, Q3 and Q8.
The operation of the bandgap reference circuit 120 is described
above. However, the bandgap reference circuit of FIG. 5 also
incorporates a gain stage with bipolar transistor Q8. In order to
incorporate a gain stage, the collector of bipolar transistor Q3 is
coupled to the base of bipolar transistor Q8. The constant bandgap
reference voltage generated at the collector of bipolar transistor
Q3 controls the base of bipolar transistor Q8 resulting in a signal
at the emitter of bipolar transistor Q8 containing a silicon
bandgap voltage with increased current density. In addition to the
bandgap reference circuit, FIG. 5 illustrates a constant current
source 140 including a start-up circuit portion. The constant
current source 140 comprises a bipolar transistor Q4 P-MOS
transistors Q5, Q7 and Q15, and resistor R4. The constant current
source 140 stabilizes operation of the thermal sensor of the
present invention over a range of V.sub.cc ranges.
[0038] In general, the constant current source 140 is derived from
the generation of the constant bandgap reference voltage. In
operation, the constant bandgap reference voltage, V.sub.bandgap,
is coupled to the base of bipolar transistor Q4. The constant
bandgap reference voltage drives the bipolar transistor Q4 to
generate a constant current flowing from the collector to the
emitter of transistor Q4 and through the resistor R4. The P-MOS
transistor Q5 is mirrored with P-MOS transistors Q7 and Q15. The
constant current flowing through resistor R4 also flows through
P-MOS transistor Q5 and is mirrored through P-MOS transistors Q7
and Q15. In a preferred embodiment, resistive element R4 equals
6020. The P-MOS transistor Q15 provides a constant current source
for the programmable V.sub.be circuit 110. Similarly, P-MOS
transistor Q7 provides a constant current source to the bandgap
reference circuit 120 through bipolar transistors Q3 and Q8.
[0039] The current source and bandgap reference voltage circuit
illustrated in FIG. 5 also comprises a start-up circuit. The
start-up circuit within the current source is required because the
bandgap reference voltage controls the current source which, in
turn, controls the bandgap reference voltage. Therefore, an
equilibrium between the bandgap reference voltage and the current
source circuit is required to ensure the proper operation of the
thermal sensor. The start-up circuit contains P-MOS transistors Q6,
Q9 and Q10. The P-MOS transistor Q9 is configured such that the
gate is coupled directly to the drain. In this configuration, the
P-MOS transistor Q9 operates as a load resistor. In general, the
start-up circuit generates a voltage for the bandgap reference
voltage circuit during initial power-up of the thermal sensor.
Specifically, during an initial power-up of the thermal sensor
circuit, transistors Q5, Q7, Q10, and Q15 are biased such that no
current flows through the respective devices. Also, during the
initial power-up state, the P-MOS transistor Q9 is biased to
conduct current thereby supplying a low voltage level to the gate
of P-MOS transistor Q6. A low voltage level at the gate of P-MOS
transistor Q6 biases the P-MOS transistor Q6 such that current
flows from the V.sub.cc to bipolar transistors Q3 and Q8. The P-MOS
transistor Q6 biases the base of bipolar transistor Q8 allowing
generation of the bandgap reference voltage.
[0040] An increase in the bandgap reference voltage driving the
base of bipolar transistor Q4 causes current to flow from the
emitter of Q4 through resistor R4. As the current density increases
through transistors Q5 and Q10, the voltage at the gate of
transistor Q6 also increases. The build up of charge at the gate of
transistor Q6 is facilitated by a large resistance generated by the
load transistor Q9. As the voltage at the gate of P-MOS transistor
Q6 raises to the pinch-off threshold voltage of the device, the
P-MOS transistor Q6 conducts no current such that current is no
longer supplied to bipolar transistors Q3 and Q8. Because of the
gain provided at the emitter of bipolar transistor Q8, current
continues to increase in the bandgap reference voltage circuit
until the collector of bipolar transistor Q3 begins to control the
base of bipolar transistor Q8. At this point, the circuit has
reached an equilibrium such that the constant bandgap reference
voltage generated supplies a constant voltage to the current
source. Also shown in FIG. 5 is a disable P-MOS transistor Q21. The
P-MOS transistor Q21 powers down, or disables, the thermal sensor
circuit for testing. The P-MOS transistor Q21 is utilized only for
disabling, and it is not required to generate the constant current
source or the bandgap reference voltage. The P-MOS transistor Q15
isolates the collector of bipolar transistor Q11 on the
programmable V.sub.be circuit from the V.sub.cc on the current
source circuit.
[0041] Referring to FIG. 6, a sense amplifier for the thermal
sensor configured in accordance with the present invention is
illustrated. In a preferred embodiment of the present invention, a
sense amplifier 160 contains three stages. The first stage and the
second stage are identical. The third stage comprises a current
buffer 600. The current buffer 600 is illustrated in FIG. 6 as a
standard logic inverter. In general, the sense amplifier 160
operates as a comparator circuit. In operation, if the
V.sub.bandgap is greater than the V.sub.out voltage, then the
output of sense amplifier 160 is a low logic level. Alternatively,
if the V.sub.out is greater than the V.sub.bandgap voltage, then
the output of sense amplifier 160 is a high logic level. The second
stage of sense amplifier 160 generates a voltage gain of signals on
lines S1 and S1#. The first stage contains PMOS transistors Q16,
Q17 and Q18, and NMOS transistors Q19 and Q20. The transistors Q19
and Q20 are constructed as a current mirror.
[0042] The voltage V.sub.out is input to the gate of PMOS
transistor Q16, and the voltage V.sub.gap is input to the gate of
PMOS transistor Q17. In operation, if the voltage V.sub.out is
greater than the V.sub.bandgap, then PMOS transistor Q17 is biased
to conduct more current than PMOS transistor Q16. Because a greater
current density flows through PMOS transistor Q17 than PMOS
transistor Q16, the voltage at line S1 rises and the voltage at
line S1# decreases. The source and gate of NMOS transistor Q19 are
connected, and the source/gate connection is controlled by the
voltage at S1#. Consequently, when the voltage at line S1#
decreases, NMOS transistor Q19 is biased to reduce the current
density flow. The voltage on line S1# is input to the gate of PMOS
transistor Q18. As the voltage on line S1# decreases, the PMOS
transistor Q18 is biased to conduct a greater current density. The
increase in current density through transistor Q18 further
amplifies the voltage difference between lines S1 and S1#. When the
V.sub.be voltage is less than the V.sub.gap voltage, the first
stage of the sense amplifier 160 operates in an analogous
manner.
[0043] The second stage of sense amplifier 160 comprises PMOS
transistors Q22, Q23 and Q24, and NMOS transistors Q25 and Q26. The
operation of the second stage of the sense amplifier 160 is
analogous to the operation of the first stage. In addition,
hysteresis is provided for the sense amplifier 160 via a feedback
path from the output of sense amplifier 160 to the programmable
V.sub.be circuit V.sub.out input of sense amplifier 160. The
hysteresis provides a more stable output signal from the sense
amplifier 160 such that voltage variations on the inputs of the
sense amplifier 160 after generation of a high output voltage level
does not cause glitches in the output signal.
[0044] For the programmable thermal sensor of the present invention
to operate well over process variations, the resistors are
constructed to have a width larger than the minimum specification
for the resistive value. All bipolar transistors in the
programmable thermal sensor contain at least double width emitters.
For the MOS transistors, long channel lengths are constructed. The
long channel lengths of the MOS transistors help stabilize the
programmable thermal sensor as well as provide noise immunity. For
the bandgap reference circuit 120, the bipolar transistor Q2 is
constructed to be ten times greater in size than the bipolar
transistor Q1. The large size differential between bipolar
transistors Q1 and Q2 provides a stable bandgap voltage
reference,
[0045] Referring to FIG. 7, a first embodiment of a microprocessor
incorporating a programmable thermal sensor configured in
accordance with the present invention is illustrated. A
microprocessor 700 contains, in part, the programmable thermal
sensor 100 and a processor unit 705. The processor unit 705 is
intended to present a broad category of microprocessor circuits
comprising a wide range of microprocessor functions. In general,
the programmable thermal sensor 100 is programmed to detect a
threshold temperature within the microprocessor 100. If the
microprocessor 700 attains the pre-programmed threshold
temperature, the programmable thermal sensor 100 generates an
interrupt. As described above, the programmable thermal sensor 100
detects the pre-programmed threshold temperature based on the
temperature of the supply voltage at the programmable thermal
sensor 100. The supply voltage across a microprocessor die can vary
as much as 8.degree. F. In a preferred embodiment of the present
invention, the programmable thermal sensor 100 is located in the
middle of the die of microprocessor 700 so as to provide the best
thermal sensing. However, placement of the programmable thermal
sensor in the middle of the die increases noise in the
microprocessor. In an alternative embodiment, several thermal
sensors are placed across the microprocessor die. In this
configuration, each thermal sensor provides an interrupt when
attaining the threshold temperature, and an average temperature is
calculated based on the several thermal sensors.
[0046] In addition to the programmable thermal sensor 100 and
processor unit 705, a microprocessor 700 contains an internal
register 735, a read only memory (ROM) 730, and a phase lock loop
(PLL) circuit 720. External to the microprocessor 700 is an
external clock 710. The external clock 710 provides a clock signal
to the PLL circuit 720. The PLL circuit 720 permits fine tuning and
variable frequency adjustment of the input clock signal.
Specifically, the PLL circuit 720 receives a value, and increases
or decreases the frequency based on the value received. The PLL
circuit 720 is intended to represent a broad category of frequency
adjustment circuits, which are well known in the art and will not
be described further. The output of the PLL circuit 720 is the
microprocessor system clock, and is input to the processor unit
705.
[0047] The programmable thermal sensor 100 is coupled to the ROM
730 and internal register 735. The ROM 730 contains a microprogram
consisting of a plurality of microcode instructions. The operation
of the microprogram within the microprocessor 700 is described more
fully below. In general, the microprogram 740 writes values
representing the threshold temperature in the internal register
735. The internal register 735 stores the threshold temperature
values and is coupled to the programmable V.sub.be circuit 110. For
example, in a preferred embodiment of the present invention, the
Vp1, Vp2 and Vp3 voltage values stored in the internal register 735
are used to program the programmable V.sub.be circuit 110 in the
manner as described above. However, the present invention is not
limited to three input voltage values in that any number of values
may be stored in the internal register 735 to program any number of
threshold temperatures. When the microprocessor 700 attains the
threshold temperature, the programmable threshold sensor generates
a comparator signal via sense amplifier 160 as described above. The
comparison signal is labeled as "interrupt" on FIG. 7. The
interrupt is input to the ROM 730 and the processor unit 705.
[0048] In response to the interrupt, the microprogram 740 generates
new values representing a new threshold temperature. The
microprogram writes the new values to the internal register 735.
For example, if the programmable thermal sensor generates an
interrupt based on a threshold temperature of 100 F., then the
microprogram may write values to the internal register 735 to
represent a threshold temperature of 110 F. In the first
embodiment, the processor unit 705 receives the interrupt signal as
a standard hardware interrupt input. In response to the interrupt,
the processor unit 705 generates a clock control value for the PLL
circuit 720. The clock signal value reduces the microprocessor
system clock frequency.
[0049] If the interrupt is again generated in response to the
microprocessor 700 attaining the new threshold temperature value,
the microprogram 740 writes a new temperature threshold value to
the internal register 735, and the processor unit 705 further
reduces the microprocessor system clock frequency. In addition, the
processor unit 705 may set a standard timer circuit such that if a
pre-determined amount of time elapses, then the processor unit 705
increases the clock frequency. Increasing the clock frequency
permits the processor unit 705 to increase performance when the
temperature of the microprocessor has decreased. In addition, to
detect further decreases in the microprocessor temperature, the
microprogram 740 may lower the threshold temperature and the
processor unit may further increase the clock frequency. Therefore,
the programmable thermal sensor of the present invention is
utilized to control the temperature by increasing and decreasing
the microprocessor clock frequency.
[0050] Referring to FIG. 8, a flow diagram for a method of
controlling the programmable thermal sensor configured in
accordance with the present invention is illustrated. The method
illustrated in the flow chart of FIG. 8 may be a microprogram such
as microprogram 740 stored in ROM 730. Upon initialization of the
microprocessor, a first threshold temperature is programmed into
the programmable thermal sensor as shown in step 800. Although the
present invention is described in conjunction with a microprocessor
integrated circuit, one skilled in the art will appreciate that the
thermal sensor of the present invention may be incorporated into
any integrated circuit. The temperature of the integrated circuit
is sensed as shown in step 810. The sensing of the integrated
circuit may be performed by the programmable thermal sensor 110 of
the present invention. The integrated circuit sensor determines
whether the temperature of the integrated circuit equals the first
threshold temperature. If the integrated circuit temperature is
equal to or greater than the threshold temperature, then the
threshold temperature is compared to a critical temperature as
shown in step 830.
[0051] The critical temperature is defined as the maximum
temperature that the integrated circuit may attain before the
integrated circuit is physically damaged. If the threshold
temperature is equal to the critical temperature, than the
integrated circuit is shut down as shown in step 860.
Alternatively, if the threshold temperature is less than the
critical temperature, than steps are taken to reduce the
temperature in the integrated circuit as shown in step 840. For
example, in a microprocessor integrated circuit, the microprocessor
system clock frequency is reduced. In addition to reducing the
system clock frequency, a message to a system user reporting the
temperature of the integrated circuit is generated. By informing
the user with the temperature information, the user may take steps
external to the integrated circuit to facilitate cooling. Next, a
new threshold temperature is programmed in the thermal sensor as
shown in step 850. The process continues wherein the thermal sensor
senses the integrated circuit temperature to detect if the
integrated circuit temperature reaches the new threshold
temperature, and based on the threshold temperature set, either
shuts down the power to the integrated circuit or executes steps to
reduce the temperature.
[0052] Referring to FIG. 9, a block diagram of a programmable
thermal sensor system configured in accordance with a second
embodiment of the present invention is illustrated. A
microprocessor 900 comprises, in part, a programmable thermal
sensor 110 and a processor unit 905. The programmable thermal
sensor 110 is configured as described above. The programmable
thermal sensor 110 is connected to a ROM 910 and an internal
register 920. The programmable thermal sensor 110 is also coupled
to external sensor logic 940. The external sensor logic 940 is
coupled to a counter 950 and an active cooling device 955. An
external clock 945 is input to a counter 950, and the output of the
counter 950 is input to a clock circuit 930. The clock circuit 930
buffers the input clock frequency to generate the microprocessor
clock for the processor unit 905. In operation, a microprogram 915,
stored in ROM 910, sets the internal register 920 to an initial
threshold temperature value. If the temperature of the
microprocessor 900 rises to the threshold temperature, an interrupt
signal is generated to the external sensor logic 940.
[0053] Upon receipt of the interrupt to the external sensor logic
940, the external sensor logic 940 programs a value to the counter
950, and activates the active cooling device 955. The active
cooling device 955 may comprise a fan or other heat dissipating
device. To activate the active cooling device 955, the external
sensor logic 940 generates a signal to turn on the active cooling
device 955 by any number of well known methods. The counter 950 is
configured as a frequency divider such that a clock frequency, from
the external clock 945, is input. The counter 950 generates a new
clock frequency based on the counter value. The programming of a
counter, such as counter 950, for use as a frequency divider is
well known in the art and will not be described further. As one
skilled in the art will recognize, the amount in which the clock
frequency may be reduced is a function of the counter selected. The
slower clock frequency is input to the clock circuit 930. The clock
circuit 930 may perform a variety of functions such as buffering,
clock distribution, and phase tuning. The system clock comprises a
reduced frequency to facilitate the cooling of the device. In
addition to triggering the external sensor logic 940, the
programmable thermal sensor also interrupts the microprogram 915.
Upon receiving the interrupt, the microprogram 915 programs the
internal register 920 to sense a new threshold temperature. If the
microprocessor 900 heats up to the new threshold temperature, the
external sensor logic 940 is again triggered, and the system clock
frequency is further reduced. The configuration illustrated in FIG.
9 provides close loop control of the microprocessor system clock
frequency, thereby automatically reducing the temperature when
overheating occurs.
[0054] Referring to FIG. 10, a block diagram of a fail safe thermal
sensor configured in accordance with the present invention is
illustrated. A fail safe thermal sensor 1010 is incorporated into a
microprocessor 1000. Although the fail safe thermal sensor 1010 is
incorporated into the microprocessor 1000, one skilled in the art
will appreciate the fail safe thermal sensor may be incorporated
into any integrated circuit. The fail safe thermal sensor 1010
contains a V.sub.be circuit 1012, a bandgap voltage reference
circuit 120, a current source 140, and a sense amplifier 160. The
bandgap voltage reference circuit 120, the current source 140 and
the sense amplifier 160 operate in accordance with the respective
circuits described above. The V.sub.be reference circuit 1012 is
equivalent to the programmable V.sub.be circuit 110, except that
the resistive value ratio is fixed. In the V.sub.be circuit 1012,
the output V.sub.be voltage is fixed based on resistive values R5,
R6, R7, R8 and R9. In a preferred embodiment of the present
invention, the resistive values R5, R6, R7, R8 and R9 are fixed to
the critical temperature. Consequently, the fail safe thermal
circuit 1010 generates an interrupt when the temperature of the
microprocessor 1000 attains the pre-programmed fixed critical
temperature.
[0055] The output of the fail safe thermal sensor 1010 is connected
to stop clock logic 1015. The stop clock logic 1015 is coupled to
the microprocessor clock circuit 1020. Upon receipt of the
interrupt of the fail safe thermal sensor 1010, the stop clock
logic 1015 halts operation of the microprocessor 1000 by inhibiting
the microprocessor clock. In addition, the stop clock logic 1015
ensures that the microprocessor 1000 finishes a system cycle
completely. The stop clock logic 1015 therefore protects loss of
data when an interrupt is generated during a microprocessor clock
cycle. A microprocessor clock circuit 1012 may comprise a simple
clock oscillator or a more complex and controllable clock
generator. The fail safe thermal sensor 1010 prohibits the
microprocessor 1000 from attaining a critical temperature, thereby
protecting the device without software control.
[0056] Referring to FIG. 11, a computer system incorporating a
microprocessor comprising thermal sensing configured in accordance
with the present invention is illustrated. A computer system 1100
contains a central processing unit (CPU) 1105 incorporating the
programmable thermal sensor 100 and the fail safe thermal sensor
1010. In a preferred embodiment, the CPU comprises a compatible
Intel microprocessor architecture, manufactured by Intel.RTM.
Corporation, the assignee of the present invention. The computer
system 1100 also contains memory 1110 and an I/O interface 1120.
The I/O interface 1120 is coupled to an output display 1130 and
input devices 1140 and 1145. In addition, I/O interface 1120 is
coupled to a mass memory device 1160. The CPU 1105, memory 1110,
I/O interface 1120, output device 1130, and input devices 1140 and
1145 are those components typically found in a computer system,
and, in fact, the computer system 1100 is intended to represent a
broad category of data processing devices. The memory 1110 stores
software for operation of the computer system 1100. Specifically,
memory 1110 stores, in part, an operating system and an interrupt
handler routine for operation in conjunction with the thermal
sensor.
[0057] Upon generation of an interrupt in the programmable thermal
sensor 100 or the fail safe thermal sensor 1010, the interrupt
handler routine 1165 is executed. The calling of an interrupt
handler routine upon generation of a hardware interrupt in a
microprocessor is well-known in the art and will not be described
further. In general, the interrupt handler routine 1165 generates a
message to the output display 1130. The message informs the user of
the computer system 1100 that the microprocessor 1105 has attained
the threshold temperature. In response, a user may alter external
environmental conditions to facilitate cooling of the CPU 1105. As
described above, the CPU 1105 sets a new threshold temperature for
the programmable thermal sensor. If the CPU 1105 temperature rises
to the new threshold temperature, another interrupt is generated.
Again, the interrupt handler routine 1165 is called to generate a
message to the user on output display 1130. If the temperature
reaches a critical temperature for which the fail safe thermal
sensor is programmed, then the fail safe thermal sensor generates
an interrupt to shut down the CPU 1105.
[0058] Although the present invention has been described in terms
of a preferred embodiment, it will be appreciated that various
modifications and alterations might be made by those skilled in the
art without departing from the spirit and scope of the invention.
The invention should therefore be measured in terms of the claims
which follow.
* * * * *