Hybrid system and method for determining performance levels based on thermal conditions within a processor

A system and method for efficient management of operating modes within an integrated circuit (IC) for optimal power and performance targets. A semiconductor chip includes one or more processing units each of which operates with respective operating parameters. One or more temperature sensors are included to measure a temperature of the one or more processing units during operation. When the measured temperature exceeds a threshold, a power manager on the chip determines a temperature headroom utilizing temperature values based on worst-case ambient temperature. When the measured temperature does not exceed the threshold, the power manager determines the temperature headroom utilizing at least one temperature value based on room ambient temperature. Following, the power manager adjusts the respective operating parameters based on at least the temperature headroom.

BACKGROUND

Field of the Invention

This invention relates to computing systems, and more particularly, to efficient management of operating modes within a semiconductor chip for optimal power and performance targets.

Description of the Relevant Art

The power consumption of modern integrated circuits (IC's) has become an increasing design issue with each generation of semiconductor chips. As power consumption increases, more costly cooling systems such as larger fans and heat sinks must be utilized in order to remove excess heat and prevent IC failure. However, cooling systems increase system costs. The IC power dissipation constraint is not only an issue for portable computers and mobile communication devices, but also for high-performance microprocessors, which may include multiple processor cores, or cores, and multiple pipelines within a core.

A power management unit (PMU) for an IC may disable portions of the IC when it detects or is otherwise informed that the portion is unused for a given period of time. Similarly, power-performance states (P-states) or dynamic voltage and frequency scaling (DVFS) techniques may be adjusted based on usage feedback of one or more processing units. These portions or processing units usually refer to general-purpose processors, graphics processors, and other processing units (although more gross or finer granularities are possible). Algorithms for the adjustments may assume worst-case thermal conditions. However, during typical usage and environment, the worst-case thermal conditions may not actually be met. Lower performance states and scaling may be selected during these times due to the assumptions in the algorithms. Therefore, available performance enhancements are not used. Changes to the algorithms may provide results that are not deterministic.

In view of the above, efficient methods and systems for efficient management of operating modes within an IC for optimal power and performance targets are desired.

SUMMARY OF EMBODIMENTS

Systems and methods for efficient management of operating modes within an IC for optimal power and performance targets are contemplated.

In various embodiments, a semiconductor chip includes one or more processing units each of which operates with respective operating parameters. The operating parameters may include power performance states (P-states) for a given processing unit or dynamic voltage and frequency scaling (DVFS) parameters for multiple processing units. One or more temperature sensors are included to measure a temperature of the one or more processing units during operation.

A power manager on the semiconductor chip determines whether or not the measured temperature exceeds a threshold. In various embodiments, the threshold is a difference between a maximum temperature limit and an under-reporting error of the temperature sensors. The maximum temperature limit may be the worst-case external ambient temperature. When the measured temperature exceeds the threshold, the power manager determines a temperature headroom utilizing temperature values based on worst-case ambient temperature.

When the measured temperature does not exceed the threshold, the power manager determines the temperature headroom utilizing at least one temperature value based on room ambient temperature. The power manager may utilize the maximum temperature limit, a measured ambient temperature and reporting errors of the one or more temperature sensors. Following, the power manager adjusts the respective operating parameters based on at least the temperature headroom.

These and other embodiments will be further appreciated upon reference to the following description and drawings.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, one having ordinary skill in the art should recognize that the invention might be practiced without these specific details. In some instances, well-known circuits, structures, and techniques have not been shown in detail to avoid obscuring the present invention.

It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to other elements.

In the detailed description that follows, references to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described includes a particular feature, structure, or characteristic. However, it is to be understood that not every embodiment necessarily includes the particular feature, structure, mode of operation, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Alternate embodiments is devised without departing from the scope of the disclosure, and well-known elements of the disclosure may not be described in detail or is omitted so as not to obscure the relevant details. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. In addition, the description refers to particular embodiments as having particular characteristics or performing particular actions using terms such as “does”, “is”, “uses”, “utilizes”, or otherwise. However, it is to be understood that various embodiments do not have the described characteristics or perform the described actions. Rather, alternate embodiments are devised without departing from the scope of the disclosure as noted above.

In addition to the above, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. For example, as used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Furthermore, as used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words “include”, “including”, and “includes” mean including, but not limited to. As used in the appended claims, these terms do not foreclose additional structure or steps. Consider a claim that recites: “A computing system comprising one or more processor cores . . . . ” Such a claim does not foreclose the computing system from including additional components (e.g., a GPU, one or more memory devices).

“Based On.” As used herein, this term is used to describe one or more factors that affect a determination. This term does not foreclose additional factors that affect a determination. That is, a determination is solely based on those factors or based, at least in part, on those factors. Consider the phrase “determine A based on B.” While B is a factor that affects the determination of A, such a phrase does not foreclose the determination of A from also being based on C. In other instances, A is determined based solely on B.

For semiconductor chips, the thermal design power (TDP) represents a maximum amount of power a cooling system in a computer is able to dissipate. The TDP may also be referred to as a thermal design point. In one example, a cooling system for a laptop processor may be designed for a 20 watt TDP. Therefore, it has been determined that the cooling system is able to dissipate 20 watts without exceeding the maximum junction temperature for transistors within the laptop processor. A power target may be assigned to a semiconductor chip, such as the laptop processor. The power target is a thermal design power value for the die of the semiconductor chip.

Typically, the semiconductor chip is able to dissipate a maximum power, which is larger than the thermal design power (TDP). To prevent failure, the semiconductor chip operates within the TDP value. This TDP value may be used within logic in a power management unit to select one or more operating modes. The power management unit may also be referred to as a power manager. The power manager may be on-chip, but alternatively, the power manager may be located off-chip.

An operational voltage and clock frequency combination may be chosen by the power manager based at least on the TDP value and an estimated power consumption value. This combination of operational voltage and clock frequency may be referred to as a power-performance state (P-state). Alternatively, the semiconductor chip may be a system-on-a-chip (SOC) with multiple processing units, such as general-purpose processing units (CPUs), graphics processing units (GPUs), and other types of processing units. Each of the processing units may have a respective P-state and the power manager utilizes dynamic voltage and frequency scaling (DVFS) techniques for selecting operational parameters for the multiple processing units.

The microarchitecture and circuit-level design techniques for balancing power consumption and performance of the semiconductor chip are aided by efforts to estimate the power consumption of processing units within the semiconductor chip in real-time. Methods for estimating power consumption for the one or more processing units in the semiconductor chip in real-time include measuring an activity level of the processing units.

While running one or more software applications, the real-time estimated power consumption of a processing unit is conveyed to the power manager. The power manager may include one or more units with control logic for balancing reduced power consumption and increased performance for the semiconductor chip. For a given processing unit, the power manager may select one discrete power-performance state (P-state) from several given discrete P-states.

The P-state selected by the power manager may be between a maximum performance state and a minimum power state. The maximum performance state includes a maximum operating clock frequency and the minimum power state includes a minimum operating clock frequency. The intermediate discrete power-performance states (P-states) include given scaled values for a combination of the operating frequency and the operational voltage. An illustration of transitioning between the P-states is provided below.

Referring toFIG. 1, one embodiment of power-performance state transitions100for a semiconductor chip is shown. Two curves are shown in the diagram showing non-linear (e.g., cubic or quadratic) relationships between power versus voltage and frequency versus voltage. Five discrete power-performance states (P-states) are shown in the diagram denoted as P0to P4. A small number of discrete P-states are shown to simplify the diagram. Although only five discrete P-states are shown, it is well known another number of discrete P-states may be supported.

In the diagram shown, the P-state P4may correspond to a discrete state with a lowest performance of all the supported discrete states and comprises the lowest operational frequency. In addition, the P-state P4may correspond to a discrete state with a lowest power consumption of all the supported discrete states and comprises the lowest operational voltage. On the other hand, the P-state P0may correspond to a discrete state with a highest performance of all the supported discrete states and comprises the highest operational frequency. In addition, the P-state P0may correspond to a discrete state with a highest power consumption of all the supported discrete states and comprises the highest operational voltage. Typically, the endpoint discrete states represented by P-states P0and P4define a region of predictable performance. Therefore, configuring the semiconductor chip to support multiple P-states, or operating points, along the non-linear frequency versus voltage curve may provide stable, optimal utilization of power and delivery of performance for the semiconductor chip, such as a processor. The management of the P-states may conform to an industry standard such as the Advanced Configuration and Power Interface (ACPI) standard, originally developed by Intel Corp., Microsoft Corp., and Toshiba Corp., but development also now includes Hewlett-Packard Corp. and Phoenix Corp. The standard was last published as Revision 5.0a on Nov. 13, 2013.

As shown in the diagram, a power target1may be chosen for the chip, wherein the power target1represents the TDP value for the chip. As described earlier, a thermal design power (TDP) may represent an amount of power that a cooling system is able to dissipate without exceeding the maximum junction temperature for transistors within the chip. As shown inFIG. 1, the power target1corresponds to a data point A on the power versus voltage non-linear curve. Data point A corresponds to an operating voltage V2. Projecting data point A onto the non-linear frequency versus voltage curve with respect to the operating voltage V2provides data point A′. The data point A′ corresponds to an operating frequency F2. The operating point represented by the combination of the operating voltage V2and the operating frequency F2may provide an optimal utilization of power and delivery of performance for the chip.

As described above and shown in the diagram, an operating point for power target1is identified by data point A′. However, this operating point is not represented by a discrete P-state on the power versus frequency curve. The data point A′ is located between the P-states P1and P2. In order to reduce power consumption, the P-state P2may be chosen as an initial operating point for the corresponding chip. A corresponding combination of the operating voltage V1and the operating frequency F1may be the resulting chosen operating point.

A chip, such as a processor, may continue processing workloads utilizing an initially assigned P-state until either (i) the workload significantly changes which causes a significant change in a reported activity level or (ii) a power consumption tracking value reaches a given threshold. For example, if a processor is executing instructions for a workload that causes a consistent activity level over time, the accumulated effect of the workload may cause a power detection system within the processor to reach a given high threshold. This threshold may indicate the processor is generating significant heat and the power should be reduced. In one embodiment, a power manager, which may be located within the processor, may detect this condition and accordingly choose a different P-state corresponding to a lower power-performance operating point.

A “throttle” of a P-state includes decrementing the currently selected P-state by one P-state to a lower power consumption P-state. In contrast, a “boost” of a P-state includes incrementing the currently selected P-state by one P-state to a higher performance P-state. Throttling the P-state P2includes transitioning the currently selected P-state P2to the lower power-performance state P3. A simple illustration of boosting and throttling a given P-state, such as the P-state P2as an example, is shown inFIG. 1. In some embodiments, each boost operation and each throttle operation may cause a currently selected P-state to transition by two or more P-states when the logic supports this added complexity. The P-state transitions may be controlled by logic within a power manager, and thereby is a self-contained system. However, the power manager may also be an external unit.

Turning toFIG. 2, one embodiment of a generalized block diagram of a semiconductor chip200is shown. Die202may comprise a processing block210coupled to a power management unit240. In some embodiments, the power management unit240is located on the die202. In other embodiments, the power management unit202is located off-chip as shown. The processing block210may comprise processing units220a-220d. Each one of the processing units220a-220dmay operate on a separate voltage plane. Accordingly, each one of the processing units220a-220dmay be coupled to a separate and respective one of the voltage regulators212a-212d. Interfaces for die202used to communicate with other components such as a memory controller, a network interface card (NIC), peripheral devices, and so forth, are not shown for ease of illustration. Any transistor family may be use to implement die202. Examples include metal oxide semiconductor field effect transistors (MOSFETs) and bipolar junction transistors (BJTs).

In one embodiment, each one of the processing units220a-220dmay be a processor, such as general-purpose processors, graphics processors, digital signal processing (DSP) cores, special-purpose coprocessors, and so forth. Alternatively, each one of the processing units220a-220dmay be an application specific integrated circuit (ASIC). Each one of the processing units220a-220dthat is a general-purpose processor may include one or more general-purpose cores. Each core may include circuitry for executing instructions according to a predefined instruction set. For example, the x86 instruction set architecture (ISA) may be selected. Alternatively, the x86-64®, ARM®, Alpha®, SPARC®, PowerPC®, MIPS®, PA-RISC®, or any other instruction set architecture may be selected. Generally, processor cores access a cache memory subsystem for data and instructions.

Each one of the processing units220a-220dthat is a graphics processing unit (GPU) typically includes one or more cores with a parallel architecture, such as a single instruction multiple data (SIMD) core. The cores may utilize very wide single instruction multiple data (SIMD) architectures to achieve high throughput in image-rendering applications. The cores may access dedicated storage buffers for data and instructions. The GPU may be a dedicated graphics-rendering device for a personal computer, a workstation, or a video game console.

A power target, such as the thermal design power (TDP), may be assigned to die202. It has been determined that the cooling system is able to dissipate the TDP value without exceeding the maximum junction temperature for transistors within the processor. In various embodiments, the power management unit240may associate a total number of power credits for die202to the TDP value for die202. The power management unit240may allocate a separate given number of power credits to each one of the processing units220a-220d. A sum of the associated power credits equals the total number of power credits for die202. Designers may determine each of the associated number of power credits for the processing units and the total number of power credits during chip development and testing. The power management unit240may be configured to adjust the number of power credits for each one of the processing units220a-220dover time. These adjustments may be based on a power profile conveyed from each one of the processing units220a-220dto the power management unit240.

For example, each one of the processing units220a-220dmay determine a corresponding power consumption number during each given time interval. Any of a variety of techniques may be utilized to determine power consumption of a given one of the processing units220a-220d.

In some embodiments, one or more of the processing units220a-220dmay sample a number of pre-selected signals. The selection of which signals to sample during a particular clock cycle may correspond to how well the selection correlates to the amount of switching node capacitance within a given one of the processing units220a-220d. For example, in one embodiment, clock enable signals routed to local clock distribution blocks may be the signals chosen to be sampled and to provide reliable and accurate power usage values.

Sampled data points corresponding to the sampled signals may be taken during each given intermittent cycle. Multiple samples are taken during a sample interval. The determination of the number of intermittent cycles to use may depend on the desired accuracy and confidence of the sampled data. For example, analysis including simulations and/or execution may be used to generate data on power consumption. Based on analysis, a table may be generated using both statistical analysis and measurements of both the real power consumption of an application and estimated power consumption from a sampling. In various embodiments, the table may be programmable (e.g., to adjust weights applicable to signals) in order to account for better estimates or otherwise. A confidence level and an error rate may be chosen to further develop the statistical analysis. Based on such analysis, selected signals may be chosen for sampling during operation.

In various embodiments, existing or additional logic may be added to the design for the purpose of sampling and/or maintaining counts (e.g., using flops) corresponding to these signals. These selected signals may be selected for sampling based upon a determination that they have a relatively significant impact on power consumption. For example, various clock enable signals, bus driver enables, mismatches in content-addressable memories (CAM), and CAM word-line (WL) drivers may be chosen for sampling. In one embodiment, a count may be maintained for such signals during operation (e.g., when a clock enable is asserted). Based on these counts, an estimate of power consumption corresponding to the counts may be determined. For example, a table such as that described above may be used to correlate counts with estimated power consumption. In such an embodiment, the estimated power consumption would not, for example, be based on measures of thermal conditions or current draw. Various examples of power estimation are described in patent application Ser. No. 12/101,598, filed Apr. 11, 2008, entitled “Sampling Chip Activity for Real Time Power Estimation”, the entirety of which is incorporated herein by reference.

The processing block210may send at least activity level measurements or data, such as the above described count data, to the power management unit240. These values are shown as usage measurements230inFIG. 2. Additionally, the processing block210may send sensor measured temperature values to the power management unit240. These measured temperature values are shown as sensor input232inFIG. 2. In various embodiments, the die202may utilize analog or digital thermal sensors placed throughout the die202. The thermal sensors provide information as to when the die heats up in a particular area due to increased compute activity. These sensors respond to each change in thermals, whether it's driven by a compute-related boost in power consumption in one or more of the processing units220a-220dor by an external environmental factor, such as a rise in ambient temperature. However, when an ambient temperature is not above a threshold, the temperature sensors can detect these scenarios. The resulting information is sent to the power management unit240.

As used herein, a temperature threshold used to indicate a “worst-case” temperature for the ambient environment may be referred to as the worst-case ambient temperature. The worst-case ambient temperature may also be referred to as the ambient temperature limit. For example, in some embodiments, the worst-case ambient temperature may be 35 degrees Celsius. However, other temperature thresholds may be used and are contemplated. The worst-case ambient temperature may be configurable and updated in a configuration or status register. Alternatively, the worst-case ambient temperature may be a fixed value stored in a register, a read-only memory (ROM), or other storage area. In some embodiments, a tolerance may be used to define a temperature range including the worst-case ambient temperature. The range may include one or more near-worst-case ambient temperature values. One or more of the near-worst-case temperature values in the range may be used in place of the worst-case temperature in calculations described throughout the description.

As shown, the power management unit240includes a power reporting unit242, an input adjuster unit244, a temperature reporting unit246and an operation parameter selector248. Control logic within the power reporting unit242receives the activity levels sampled or measured during a given time interval. The power reporting unit242calculates a power value from the usage measurements230received from activity monitors in the processing units220a-220d. The power reporting unit242may also calculate a leakage power value to include in a total power value. The leakage power value is dependent on a calculated temperature. The calculated temperature is determined by the temperature reporting unit246and utilizes a worst-case ambient temperature value. As described above, the worst-case ambient temperature may be a temperature threshold, or an ambient temperature limit, used to indicate a “worst-case” temperature for the ambient environment. When the sensor-measured temperature is significantly different from the calculated temperature, the calculated power value does not change.

The calculated power value is sent to the temperature reporting unit246. The temperature reporting unit246utilizes both the received calculated power value and input values from the input adjuster unit244. The input adjuster unit244receives the sensor input232, which is the sensor measured temperature value. In various embodiments, if the sensor measured temperature value exceeds a temperature threshold, then the input adjuster unit244does not alter the calculations in the temperature reporting unit246. The temperature reporting unit246receives the calculated power value from the power reporting unit242and translates the received value to a calculated die temperature value. The temperature reporting unit246may utilize a transient resistor-capacitance (RC) thermal model for the translation. The RC thermal model typically utilizes a worst-case ambient temperature. In some embodiments, the worst-case ambient temperature may be 35 degrees Celsius.

The calculated temperature value is sent to the operation parameter selector248. Alternatively, a calculated boost value is sent to the operation parameter selector248. For example, the temperature reporting unit246may determine from the calculated power value that the calculated temperature is 98 degrees Celsius. The temperature reporting unit246may send the value of 98 degrees Celsius to the operation parameter selector248. The operation parameter selector248may use the received calculated temperature value to determine the boost value, which may be the difference between the maximum temperature limit and the calculated temperature. In this example, when the maximum temperature limit is 100 degrees Celsius, the boost value is (100−98), or 2 degrees Celsius. Alternatively, the temperature reporting unit246may calculate and send the boost value to the operation parameter selector248.

The operation parameter selector248receives the calculated temperature value or the boost value, and accordingly selects a set of operation parameters for the processing units220a-220dbased on the received value. The power management unit240sends the selected operation parameters234to the die202. In various embodiments, the operation parameters234are P-state values. The selection of the operation parameters may dynamically modulate the operational voltage and operational clock frequency combination to vary power consumption of the die202such that the calculated power value causes the calculated temperature value to reach a maximum temperature value in the next time interval. Therefore, a feedback loop is created among the unit248, processing units220a-220d, and the unit242. As described earlier, the maximum temperature value may be based on the TDP and the transistor junction breakdown temperature for the die202. In some embodiments, the maximum temperature value is 100 degrees Celsius.

The translation of the calculated power value to the calculated temperature value utilizes the worst-case ambient temperature. Therefore, the temperature reporting unit246conservatively uses the assumption that the die202continually operates under worst-case temperature conditions, such as the worst-case ambient temperature. However, under thermal conditions with room ambient temperature, such as 23 degrees Celsius, the actual temperature of die202may significantly be different from each of the calculated temperature and the maximum temperature limit. For example, the difference between the worst-case ambient temperature of 35 degrees Celsius and room ambient temperature of 23 degrees Celsius is 12 degrees Celsius. The difference of 12 degrees Celsius may not be used for boosting P-states under the approach of using conservative worst-case calculations. Therefore, the feedback loop and the adjustment of the operation parameters do not increase performance of die202as available under the room ambient temperature condition. However, the measured sensor temperature may be used to adjust the conservative worst-case approach and access the additional available performance gains.

As described earlier, the processing block210may send sensor measured temperature values to the power management unit240. These measured temperature values are shown as sensor input232inFIG. 2. The die202may utilize analog or digital thermal sensors placed throughout the die202. The thermal sensors provide information as to when the die heats up in a particular area due to increased compute activity by one or more of the processing units220a-220dor by an external environmental factor, such as a rise in ambient temperature. However, when worst-case ambient temperature conditions are not a factor, the temperature sensors can also detect these scenarios.

The input adjuster unit244receives the sensor input232, which is the sensor measured temperature value. The accuracy of the on-die temperature sensors may influence the available temperature margin used for extra boosting of the operation parameters. The high temperature reporting sensors have an over-reporting error. Similarly, the low temperature reporting sensors have an under-reporting error. For example, these errors may have a magnitude of 4 degrees Celsius.

In various embodiments, the sensor measured temperature value sent to the input adjuster unit244is compared to a temperature threshold. In some embodiments, the temperature threshold is a difference between the maximum temperature limit and the magnitude of the under-reporting error of the temperature sensors. Again, the maximum temperature value may be based on the TDP and the transistor junction breakdown temperature for the die202. In some embodiments, the maximum temperature value is 100 degrees Celsius. If the magnitude for under-reporting error for the on-die temperature sensors is 4 degrees Celsius, then the temperature threshold for this example is (100−4), or 96 degrees Celsius. Additionally, other formulas and values for the temperature threshold are possible and contemplated.

In various embodiments, if the sensor measured temperature value sent to the input adjuster unit244is less than a temperature threshold, then the input adjuster unit244alters the calculations in the temperature reporting unit246. The input adjuster unit244may alter the calculations in the temperature reporting unit246in multiple ways. In some embodiments, the input adjuster unit244may indicate to the temperature reporting unit246that an extra margin is to be added to a calculated boost value. In some embodiments, the extra margin is a difference between (i) a difference between the worst-case ambient temperature and the room ambient temperature and (ii) a sum of the magnitudes of the temperature sensor over-reporting error and the under-reporting error. For example, with the values used earlier, the extra margin would be (35−23)−(4+4), or 12−8, or 4 degrees Celsius. The extra margin of 4 degrees Celsius would be added to the original boost value. For example, if the temperature threshold is 96 degrees Celsius and the calculated temperature is 94 degrees Celsius, then the extra boost value of 4 degrees Celsius would be added to the original boost value of (100−94), or 6 degrees Celsius for a total boost value of (6+4), or 10 degrees Celsius. The total boost value of 10 degrees Celsius is sent to the operation parameter selector248.

As described earlier, the input adjuster unit244may alter the calculations in the temperature reporting unit246in multiple ways. One adjustment is calculating an extra boost value as described in the above description. In addition, in other embodiments, the input adjuster unit244may indicate to the temperature reporting unit246to utilize a different temperature than the worst-case ambient temperature in the transient RC thermal model used for translating the calculated power to the calculated die temperature. For example, the worst-case ambient temperature may be replaced or scaled according to the received sensor measured temperature. Additionally, the over-reporting and under-reporting sensor errors may be used for scaling.

Further, another adjustment that may be used is replacing or scaling the RC coefficients used in the transient RC thermal model. Again, the received sensor measured temperature and the over-reporting and under-reporting sensor errors may be used for scaling. Further still, the input adjuster unit244may replace or scale the calculated power value based on the received sensor measured temperature and the over-reporting and under-reporting sensor errors.

Turning now toFIG. 3, one embodiment is shown of temperature values300indicating sensor temperature accuracy. As shown, a worst-case room temperature310may have an appreciable difference330with room ambient temperature320. The room temperature difference330may be used for extra boosting of operation parameters of one or more processing units. However, the on-die temperature sensors used to determine whether to use the extra boosting include reporting errors.

The accuracy of the temperature sensors influences the available amount of extra boosting used for selecting the operation parameters. An under-reporting error340of low temperature reporting sensors reduces the available amount of extra boosting from the room temperature difference330. Additionally, an over-reporting error342of high temperature reporting sensors reduces the available amount of extra boosting from the room temperature difference330. The remaining available amount of extra boosting from the room temperature difference330is shown as the margin for performance boost344.

Referring now toFIG. 4, one embodiment of a method400for boosting performance when worst-case temperature conditions are not present is shown. For purposes of discussion, the steps in this embodiment are shown in sequential order. However, some steps may occur in a different order than shown, some steps may be performed concurrently, some steps may be combined with other steps, and some steps may be absent in another embodiment.

In block402, a semiconductor chip may receive requested time interval(s) for power reporting from an external agent, such as the operating system or another chip or computation unit. Alternatively, the semiconductor chip may have the time interval for power reporting stored in configuration and status registers, in BIOS, or in firmware. In block404, the semiconductor chip loads and processes instructions of one or more software applications. In some embodiments, the semiconductor chip may have been processing applications before receiving values for the time interval. Control logic within the semiconductor chip may sample a number of pre-selected signals. The selection of which signals to sample during a particular clock cycle may correspond to how well the selection correlates to the amount of switching node capacitance within a given one of one or more processing units on the semiconductor chip.

If the time interval has elapsed (conditional block406), then in block408, one or more on-die temperature sensors provide temperature measurements to read. The measurements may be combined into a single value, such as an average value. The measured temperature is compared to a temperature threshold. In some embodiments, the temperature threshold is a difference of a maximum temperature limit and an under-reporting sensor error. However, other values for the threshold are possible and contemplated.

If the measured temperature exceeds the threshold (conditional block410), then in block412, the temperature headroom for boosting is determined utilizing temperature values based on worst-case ambient temperature. As described earlier, a power value may be calculated from reported activity levels based on sampling selected signals. A transient RC thermal model may be used to translate the calculated power value to a calculated temperature value. The RC thermal model typically utilizes a worst-case ambient temperature. A difference between the maximum temperature limit and the calculated temperature value may be used as temperature headroom for boosting.

If the measured temperature does not exceed the threshold (conditional block410), then in block414, the temperature headroom for boosting is determined by utilizing at least one temperature value based on room ambient temperature. As described earlier, in some embodiments, an extra margin is added to a calculated boost value. The extra margin may be a difference between (i) a difference between the worst-case ambient temperature and the room ambient temperature and (ii) a sum of the magnitudes of the temperature sensor over-reporting error and the under-reporting error. For example, with the values used earlier, the extra margin would be (35−23)−(4+4), or 12−8, or 4 degrees Celsius. The extra margin of 4 degrees Celsius would be added to the original boost value. The original boost value may be the difference between the maximum temperature limit and the calculated temperature value. The sum would be the temperature headroom.

In other embodiments, determining the temperature headroom for boosting utilizes a different temperature than the worst-case ambient temperature in the transient RC thermal model used for translating the calculated power to the calculated die temperature. For example, the worst-case ambient temperature may be replaced or scaled according to the received sensor measured temperature and the over-reporting and under-reporting sensor errors. In yet other embodiments, determining the temperature headroom for boosting includes replacing or scaling the RC coefficients used in the transient RC thermal model or the calculated power value. Again, the received sensor measured temperature and the over-reporting and under-reporting sensor errors may be used for scaling. In block416, the operating parameters of one or more processing units are adjusted based on the temperature headroom.

Referring now toFIG. 5, another embodiment of a method500for boosting performance when worst-case temperature conditions are not present is shown. For purposes of discussion, the steps in this embodiment are shown in sequential order. However, some steps may occur in a different order than shown, some steps may be performed concurrently, some steps may be combined with other steps, and some steps may be absent in another embodiment.

In block502, a time interval is selected for power reporting on a semiconductor chip. Methods described earlier may be used for the selection. In block504, the semiconductor chip loads and processes instructions of one or more software applications. Control logic within the semiconductor chip may sample a number of pre-selected signals during a particular clock cycle. The selected signals may correlate to the amount of switching node capacitance within a given one of one or more processing units on the semiconductor chip.

If the time interval has elapsed (conditional block506), then in block508, a power value is calculated from reported activity levels that are based on sampling selected signals. In addition, a leakage power value may also be calculated. The power value and the leakage power value are summed to provide a total calculated power value, Pcalc. The leakage power value is dependent on a calculated temperature. The calculated temperature is determined by control logic utilizing a worst-case ambient temperature value. Therefore, when the actual ambient temperature is significantly different from the worst-case ambient temperature, the calculated power value, Pcalc, does not change.

In block510, a transient RC thermal model is used to translate the calculated power value, Pcalc, to a calculated temperature value, Tcalc. The RC thermal model utilizes a worst-case ambient temperature. In block512, one or more on-die temperature sensors provide temperature measurements to read. The measurements may be combined into a single value, such as an average value. The measured temperature, Tmeas, is compared to a temperature threshold. In some embodiments, the temperature threshold is a difference of the maximum temperature limit, Tmax, and an under-reporting sensor error, Tunder-reporting. Using values in earlier examples, Tmax is 100 degrees Celsius and the magnitude of Tunder-reporting is 4 degrees Celsius. Therefore, the threshold is (Tmax−Tunder-reporting), or (100−4), which is 96 degrees Celsius. However, other expressions for the threshold are also possible and contemplated.

If the measured temperature, Tmeas, exceeds the threshold (conditional block514), then in block516, the temperature headroom for boosting is determined by the difference between the maximum temperature limit, Tmax, and the calculated temperature value, Tcalc, or (Tmax−Tcalc). Using values in earlier examples, Tmax is 100 degrees Celsius and the threshold is 96 degrees Celsius. The value Tmeas may be 98 degrees Celsius and exceeds the threshold of 96 degrees Celsius. Therefore, the temperature headroom is (Tmax−Tcalc). The calculated temperature may be at Tmax or very close, which does not provide a significant temperature headroom for boosting.

If the measured temperature, Tmeas, does not exceed the threshold (conditional block514), then in block518, the temperature headroom for boosting is based on at least a maximum temperature limit, Tmax; room ambient temperature, Troom-ambient; and the on-die sensor errors. The temperature headroom may be represented by the expression:
Tmax−(Tcalc−Textra-margin)=(Tmax−Tcalc)+Textra-margin

The value Textra-margin may be represented by the expression:
(Tworst-case-ambient−Troom-ambient)−Tunder-reporting−Tover-reporting=(Tworst-case-ambient−Troom-ambient)−(|Tunder-reporting|+|Tover-reporting|)

Using the values of earlier examples, Tmax is 100 degrees Celsius and the threshold is 96 degrees Celsius. The value Tmeas may be 94 degrees Celsius and does not exceed the threshold of 96 degrees Celsius. Therefore, the temperature headroom is (Tmax−Tcalc)+Textra-margin, wherein the value Textra-margin is (35−23)−(4+4)=12−8=4 degrees Celsius. The temperature headroom becomes (100−94)+4=10 degrees Celsius. In block520, the operating parameters of one or more processing units are adjusted based on the temperature headroom and possibly on the allocation of power credits.

It is noted that the above-described embodiments may comprise software. In such an embodiment, the program instructions that implement the methods and/or mechanisms may be conveyed or stored on a computer readable medium. Numerous types of media which are configured to store program instructions are available and include hard disks, floppy disks, CD-ROM, DVD, flash memory, Programmable ROMs (PROM), random access memory (RAM), and various other forms of volatile or non-volatile storage. Generally speaking, a computer accessible storage medium may include any storage media accessible by a computer during use to provide instructions and/or data to the computer. For example, a computer accessible storage medium may include storage media such as magnetic or optical media, e.g., disk (fixed or removable), tape, CD-ROM, or DVD-ROM, CD-R, CD-RW, DVD-R, DVD-RW, or Blu-Ray. Storage media may further include volatile or non-volatile memory media such as RAM (e.g. synchronous dynamic RAM (SDRAM), double data rate (DDR, DDR2, DDR3, etc.) SDRAM, low-power DDR (LPDDR2, etc.) SDRAM, Rambus DRAM (RDRAM), static RAM (SRAM), etc.), ROM, Flash memory, non-volatile memory (e.g. Flash memory) accessible via a peripheral interface such as the Universal Serial Bus (USB) interface, etc. Storage media may include microelectromechanical systems (MEMS), as well as storage media accessible via a communication medium such as a network and/or a wireless link.

Additionally, program instructions may comprise behavioral-level description or register-transfer level (RTL) descriptions of the hardware functionality in a high level programming language such as C, or a design language (HDL) such as Verilog, VHDL, or database format such as GDS II stream format (GDSII). In some cases the description may be read by a synthesis tool, which may synthesize the description to produce a netlist comprising a list of gates from a synthesis library. The netlist comprises a set of gates, which also represent the functionality of the hardware comprising the system. The netlist may then be placed and routed to produce a data set describing geometric shapes to be applied to masks. The masks may then be used in various semiconductor fabrication steps to produce a semiconductor circuit or circuits corresponding to the system. Alternatively, the instructions on the computer accessible storage medium may be the netlist (with or without the synthesis library) or the data set, as desired. Additionally, the instructions may be utilized for purposes of emulation by a hardware based type emulator from such vendors as Cadence®, EVE®, and Mentor Graphics®.