Patent Publication Number: US-2010131787-A1

Title: Adaptive Power Consumption Techniques

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a Continuation of U.S. patent pplication Ser. No. 11/452,462 filed Jun. 13, 2006, which is a Divisional of U.S. patent application Ser. No. 10/226,708 filed Aug. 22, 2002, both of which are incorporate herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Portable electronic devices rely on batteries to provide the necessary power for the operation of the device. Consumers using the portable devices want to be able to use the devices for longer time periods in between having to recharge the batteries. As such, there is a continual effort to increase battery performance and to perform the operations in more energy efficient ways, even as the applications performed by the devices become more sophisticated, and in some cases, require more power. 
     The central processing unit (CPU) is generally the largest consumer of power for the portable computing devices. However, the power consumption of the CPU is generally not capable of being modified for the various applications being executed. That is, there is one-size fits all approach for the power consumption of the microprocessors for the devices even though some applications require only a fraction of the CPU power. For example when watching a movie on a laptop computer having a digital video disc (DVD) player, a clock speed of only up to about 20% of the operating clock speed of the CPU may be necessary. While there has been some attempts to reduce the power consumption of microprocessors, none allow for the power consumption to be modified based upon a predicted application demand. Furthermore, when the operating system is placed into an idle mode, the CPU clock frequency does not change. Therefore, the power consumption of the CPU remains unnecessarily high. 
     As a result, there is a need to solve the problems of the prior art to provide a method and apparatus for reducing the power consumption of microprocessors, such as CPUs, where the power consumed by the CPU is based upon the application being executed. 
     SUMMARY OF THE INVENTION 
     Broadly speaking, the present invention fills these needs by providing a method and apparatus for reducing power consumption of microprocessors. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, a system, or a device. Several inventive embodiments of the present invention are described below. 
     This invention relates generally to power management and more particularly to a method and apparatus to reduce the power consumption of portable devices to increase battery life by dynamically modifying a clock speed of a processor. 
     In one aspect of the invention a method for adapted power consumption of a microprocessor based upon an application demand is provided. The method initiates with determining an application demand based upon a current processing operation. Then, a time interval associated with the application demand is determined. Next, unnecessary power consuming functions for the application demand are determined. Then, a clock frequency for the unnecessary power consuming functions is reduced for the time interval. In one embodiment, the power is terminated to the unnecessary power consuming functions. In another embodiment, the clock frequency of the microprocessor is adjusted for at least a portion of the time interval. 
     In another aspect of the invention, a method of adapting processing power of a microprocessor is provided. The method initiates with tracking a load level for a time interval. Then, idle time during the time interval is monitored. Next, a percentage of maximum processing power of the microprocessor sufficient to power the load level is determined. Then, the processing power of the microprocessor is adjusted to the determined percentage. In one embodiment, a plurality of load levels are tracked. In another embodiment, the plurality of load levels are associated with the frames of a motion picture expert group (MPEG) standard. 
     In yet another aspect of the invention, a program interface for adapting power consumption of a computer system is provided. The program interface includes an interface for adjusting a clock frequency of a microprocessor. The interface enables the adjustment of the clock frequency in response to a determined processing load level, wherein the adjustment of the clock frequency is defined to vary as a function of time. In one embodiment, the program interface includes an interface for adjusting a voltage of a microprocessor. In this embodiment, the interface enables the adjustment of the voltage in response to a determined processing load level, wherein the adjustment of the voltage is defined to vary as a function of time. 
     In still yet another aspect of the invention, processor instructions for adapting power consumption of a computer system are provided. The processor instructions include computer code configured to trigger an adjustment of a clock frequency of a microprocessor. The computer code enables the adjustment of the clock frequency in response to a determined processing load level, wherein the adjustment of the clock frequency is defined to vary as a function of time. In one embodiment, the processor instructions include computer code configured to trigger an adjustment of a voltage of a microprocessor. In this embodiment, the computer code enables the adjustment of the voltage in response to a determined processing load level, wherein the adjustment of the voltage is defined to vary as a function of time. 
     In another aspect of the invention, a processor apparatus is provided. The processor apparatus includes an instruction decoder configured to identify an instruction that writes a value to a control register. The control register affects a clock frequency used to clock the processor apparatus. In one embodiment, the processor apparatus includes an instruction decoder configured to identify an instruction that writes a value to a control register. In this embodiment, the control register affects a voltage source used to supply power to the processor apparatus. 
     Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention are illustrated by way of example and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: 
         FIG. 1  shows a high level schematic diagram of a system having microprocessors enabled to modulate power consumption based upon application demand in accordance with one embodiment of the invention. 
         FIG. 2  shows a simplified schematic diagram of the system of  FIG. 1  providing a more detailed description of the power adjusting interface for a microprocessor in accordance with one embodiment of the invention. 
         FIG. 3  shows a simplified schematic diagram of an interface configured to adapt power consumption of a microprocessor in accordance with one embodiment of the invention. 
         FIG. 4  shows a table displaying the different frames of the motion picture expert group (MPEG) standard where time intervals between each of the frames are associated with a frequency that is accommodated by a microprocessor in accordance with one embodiment of the invention. 
         FIG. 5  shows a flowchart diagram of the method operations for adapting power consumption of a microprocessor based upon an application demand in accordance with one embodiment of the invention. 
         FIG. 6  shows a flowchart of the method operations for adapting the processing power of a microprocessor for a load level in accordance with one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with these embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it is understood that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention. 
     An invention is described for an apparatus and method for adapting power consumption of a microprocessor based on an application demand. In particular, the embodiments of the present invention provide a method and apparatus that minimizes the power consumption of a microprocessor by predicting a load level based upon application demand. In one embodiment, predictive knowledge accessed through the application level, which is based upon the process operation being currently executed, determines the load level necessary for an upcoming time period. It should be appreciated that the application uses predictive knowledge of what is happening to modify a clock speed or voltage supplied to a microprocessor, rather scaling based upon past performance. The forward looking approach described herein is enabled through a feedback loop between the microprocessor and the application level in one embodiment. The predictive knowledge can be used to enable selected functions, or domains within a processor, to have their clock frequency set to zero. Alternatively, the microprocessor speed can be throttled up or down by setting a clock frequency and/or voltage based upon a load required over an interval of time. 
       FIG. 1  is a high level schematic diagram of a system having microprocessors enabled to modulate power consumption based upon application demand in accordance with one embodiment of the invention. Device  100  includes central processing unit (CPU)  102 , memory  110 , and graphics processing unit (GPU)  106 , each in communication with a support chipset  108  (e.g., Northbridge and Southbridge chips). As is well known, the chipset  108  controls interaction with memory  110 , the peripheral component interconnect (PCT) bus, level 2 cache, and all accelerated graphics port (AGP) activities. Therefore, the chipset  108  couples to graphics card  118  by way of an AGP bus. In one embodiment, Northbridge chip set  108  can also include function as an integrated graphics processor (IGP). In other embodiments, the chipset  108  can be incorporated in the CPU  102  and/or the GPU  106 . CPU  102  includes control register  114  which responds to instructions for controlling the clock speed of the CPU. Basic input/output system (BIOS)  112  is also included. 
     Still referring to  FIG. 1 , power adjusting interfaces  104   a  and  104   b  are in communication with CPU  102  and GPU  106 , respectively. It should be appreciated that GPU  106  also includes a control register responding to instructions for controlling the clock speed of the GPU. In one embodiment, power adjusting interfaces  104   a  and  104   b  are application program interfaces (API). In another embodiment, power adjusting interfaces  104   a  and  104   b  are operating system (OS) interfaces. In yet another embodiment, power adjusting interfaces  104   a  and  104   b  are new processor instructions configured to set the clock frequency of the processor. Thus, the interfaces described herein include a hook to the application being executed as the application provides the means to determine future demands for the CPU&#39;s performance. In turn, the voltage and clock speed of the CPU can be modulated for a specified time interval associated with the predicted application demand. It will be apparent to one skilled in the art that while a CPU is used as an example here, the embodiments described herein apply to any suitable processor. 
       FIG. 2  is a schematic diagram of the system of  FIG. 1  providing a more detailed description of the power adjusting interface for a processor in accordance with one embodiment of the invention. Here, device  100  includes chipset  108  in communication with CPU  102 , GPU  106  and memory  110 . BIOS  112  is also included. Power adjusting interface  104   a  includes complementary metal oxide semiconductor (CMOS) electrically erasable programmable read only memory (EEPROM)  116  and a software application program interface (API)  118 . Application program  120  is in communication with API  118  so that the future application demands can be communicated to API  118 , which in turn provides the application demand to software in the EEPROM  116 . Consequently, software in the EEPROM  116  can set the frequency for CPU  102  by writing data to control register  114  which controls the clock speed of the CPU. In one embodiment, power adjusting interfaces  104   a  and  104   b  control the voltage supplied to CPU  102  and GPU  106 , respectively. In another embodiment, power adjusting interface  104   b  can include the same components as described with respect to power adjusting interface  104   a.  It should be appreciated that power adjusting interfaces  104   a  and  104   b  can be configured differently as discussed in more detail with respect to  FIG. 3 . 
     It will be apparent to one skilled in the art that device  100  of  FIGS. 1 and 2  can be any suitable electronic device having a microprocessor. For example, device  100  may be a portable device such as a laptop computer, cellular phone, personal digital assistant, etc. While the adaptive power consumption properties disclosed herein enhance the battery life of the portable electronic devices, the invention is not limited to portable electronic devices. For example device  100  can be associated with a desktop computer. While battery life is not an issue with a desktop system, the embodiments described herein will conserve energy. Additionally, power adjusting interface  104  can be associated with any suitable processor including a CPU, a GPU, a network processing unit (NPU), a storage processing unit (SPU), etc. Various processing units are described in U.S. patent application entitle “Method and Apparatus For Providing An Integrated Network of Processors”, filed on May 13, 2002, with Ser. No. 10/144,658, incorporated herein by reference. 
       FIG. 3  is a schematic diagram of an interface configured to adapt power consumption of a microprocessor in accordance with one embodiment of the invention. Microprocessor  122  includes control register  124  where the clock frequency is set. Interface  126  is in communication with microprocessor  122 . More particularly, interface  126  is configured to write to control register  124  to adapt the power consumption of microprocessor  122 . The communication link between interface  126  and application  120  provides the feedback necessary to adapt the power consumption of microprocessor  122  to the load level. In one embodiment, application  120  communicates with interface  126  in the form of a driver and/or an application program interface (API). In another embodiment, the instructions providing data to the control register are decoded by an instruction decoder contained within microprocessor  122 . The instruction decoder is configured to identify special instruction that writes a value to control register  124 . One skilled in the art will appreciate that the instruction can be a privileged instruction in one embodiment. It should be appreciated that the feedback of the forward looking application demand allows for the power, i.e., clock frequency, to behave as a “just in time’ power supply or clock frequency for each level of application demand. 
     It will be apparent to one skilled in the art that interface  126  can be in the form of an API as discussed with reference to  FIG. 2  or an operating system interface. For example the operating system interface could put microprocessor  122  in a lower power state when the operating system (OS) is in an idle mode. The application specific throttling provided by interface  126  can place microprocessor  122  in a low power mode, however, the microprocessor is enabled to be returned to a high power mode fast enough without causing any delays. That is, for a higher application demand following the low power mode the microprocessor wakes up so that no delays are caused. Where interface  126  is an API, the clock speed, i.e., frequency can be supplied through a frequency plot or a table specifying the frequency for specified time periods. In one embodiment, the API is at the ring  3  level which could call a ring  0  driver. One skilled in the art will appreciate that the table or graphs supplied help eliminate any overhead caused by switching between modes. In one embodiment, interface  126  is a set of instructions for adapting the power level or clock frequency of microprocessor  122 . 
       FIG. 4  is a table displaying the different frames of the motion picture expert group (MPEG) standard where time intervals between each of the frames are associated with a frequency that is accommodated by a microprocessor in accordance with one embodiment of the invention. Significant power savings can be realized for digital video disc (DVD) playback on a portable computer with this embodiment. As is generally known, the MPEG compression technique includes three types of frames, the intra (I) frame, the predicted (P) frame and the bi-directional (B) frame. Here, the inter frame load during decode can be monitored to adapt power consumption per frame. With the MPEG standard, the processing power demanded by each frame varies drastically between the three (I, P, and B) frame types. That is, the load for the bi-directional frames is significantly less than the load for the intra frames when using a GPU based MPEG decode accelerator. Generally, for the case of doing everything on the CPU, the loads are reversed. Accordingly, the microprocessor can be throttled back for the bi-directional frames and brought back up for the intra frames. 
     In one embodiment, the table of  FIG. 4  can be supplied through the interface of  FIGS. 2 and 3 . Row  130  contains frequencies (f I , f P , and f B ) that the microprocessor will run at for the I, P, and B frames, respectively. Column  132  represents the time periods for running the specified frequency for each frame. For example, time period x o  through x n  correspond to successive I frames O-n. The same is true for the time periods associated with the P and B frames. Alternatively, rather than having a plurality of time periods for each successive frame, a single time period can be applied for the each frame type. For example table  128  would consist of row  134  where one time period is associated with each frame type. The interface  126  can be used to set the table  128  values once for a particular video, or update the values periodically. Updating the table  128  values periodically can account for varying decode time periods. For example the decode time periods can be set by using a predictive filter (i.e., a filter that generates an estimate of a future value based on past values), as known in the art of digital signal processing. 
     Still referring to  FIG. 4 , once a video frame is decoded, the microprocessor can go into a sleep mode where only enough power is supplied to keep time. For example the time to decode a video frame associate with the MPEG standard is about 3 milliseconds when using a currently available GPU-based MPEG decode accelerator. A typical display rate of 24 frames per second, translates to each frame being displayed for 42 milliseconds. Therefore, the microprocessor can go into the sleep mode for 39 milliseconds in between frames as instructed through the interface. The power savings add up to a significant level over a period of time where a movie is watched on a portable computer. In one embodiment, the microprocessor transitions out of the sleep mode within one millisecond. Accordingly, a heuristic can be provided through the interface to throttle down the CPU and the GPU based upon a percent of idle time per frame. Furthermore, the GPU can turn off unused hardware modules during DVD playback operation. For example where the portable computer is operating in a full-screen mode the 2-dimensional or 3-dimensional graphics pipelines are not needed. Thus, the interface can be configured to power down the unnecessary hardware modules. It should be appreciated that the example of the interface with respect to the DVD playback application is for exemplary purposes and is not meant to be limiting as the interface can be configured to adapt the power of a microprocessor for any suitable application. 
       FIG. 5  is a flowchart diagram of the method operations for adapting power consumption of a microprocessor based upon an application demand in accordance with one embodiment of the invention. The method initiates with operation  140  where an application demand is determined. Here, the application demand is based upon a current processing operation. For example the processing operation can be DVD playback of a movie, a computer game, video editing, word processing, etc. 
     The method then advances to operation  142  where a time interval associated with the application demand is determined. The time interval is the period of time that a certain application demand will be required for, such as the time period in between frames of a DVD playback of a movie. The method then proceeds to operation  144  where unnecessary power consuming functions are determined. For example the 3-dimesional pipeline for a GPU can be turned off if the computer is only doing DVD playback that does not require any 3-dimesional processing. The method then moves to operation  146  where a clock frequency of a microprocessor is adjusted for the unnecessary power consuming functions. In another embodiment, the clock frequency of the microprocessor is adjusted for a portion of the determined time interval. 
       FIG. 6  is a flowchart of the method operations for adapting the processing power of a microprocessor for a load level in accordance with one embodiment of the invention. The method initiates with operation  150  where a load level is tracked for a time interval. Here, the load level is associated with an application demand on a microprocessor. In one embodiment, a plurality of load levels can be monitored, such as the load levels for the different frames of the MPEG standard discussed with reference to  FIG. 4 . The method then advances to operation  152  where idle time during the time interval is monitored. Here, the microprocessor can complete an operation, such as decoding a frame within a certain time that is less than the time interval needed for the frame to be presented. Thus, the microprocessor will sit idle at full power for a period of time. The method then moves to operation  154  where a percentage of maximum processing power of the microprocessor that is sufficient for the load level is determined. For example the microprocessor can sit in a sleep mode and only needs to be supplied with enough power to track time when it is idle. Alternatively, the microprocessor may require some percentage of power that is less than full (100%) power. 
     The method then proceeds to operation  156  where the processing power of the microprocessor is adjusted to the determined percentage. Here an interface can be provided where instructions are sent to a control register to modify the clock speed or voltage of the microprocessor as discussed with reference to  FIGS. 1-4 . The interface can be an API or an OS interface and the microprocessor can be a CPU, GPU, NPU, or a SPU. In one embodiment, an API can vary the clock frequency or voltage as a function of time, with reference to a synchronous event, such as the decoding of video frames as described above. 
     In summary, the embodiments described above allow for adapting the power consumption of a microprocessor based upon need. The need is determined by an application demand which is communicated to the microprocessor through an interface configured to write into a frequency control register of the microprocessor. In one embodiment, the control register is a floating point control register included with some commercially available microprocessors. With respect to DVD playback, the embodiments described herein can enable adapting the microprocessor to go into a sleep mode between the presentation of video frames allowing for a significant power savings. 
     In turn, the battery life between charging is extended. Consequently, the viewing of movies can be easily accomplished on a portable computer without the necessity of having to switch multiple battery packs to complete the viewing of the movie. 
     With the above embodiments in mind, it should be understood that the invention may employ various computer-implemented operations involving data stored in computer systems. These operations include operations requiring physical manipulation 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. Further, the manipulations performed are often referred to in terms, such as producing, identifying, determining, or comparing. 
     Any of the operations described herein that form part of the invention are useful machine operations. The invention also relates to a device or an apparatus for performing these operations. The apparatus may be specially constructed for the required purposes, or it may be a general purpose computer selectively activated or configured by a computer program stored in the computer. In particular, various general purpose machines may be used with computer programs written in accordance with the teachings herein, or it may be more convenient to construct a more specialized apparatus to perform the required operations. The invention can also be embodied as computer readable code on a computer readable medium. The computer readable medium is any data storage device that can store data which can be there after be read by a computer system. Examples of the computer readable medium include hard drives, network attached storage (NAS), read-only-memory, random-access-memory, CD-ROMs, CD-Rs, CD-RWs, magnetic tapes, and other optical and non-optical data storage devices. The computer readable medium can also be distributed over a network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. 
     The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.