Abstract:
Methods and apparatuses are provided for controlling power consumption in a processor (or computational unit thereof). The method comprises monitoring power consumption in a processor (or computational unit) and determining that the power consumption of the processor (or computational unit) exceeds a threshold. Thereafter, instruction issuance if modified (such as by slowing or ceasing instruction issuance) within the processor (or computational unit) until the power consumption is below the threshold. The apparatus comprises a power consumption monitor for determining when power consumption within the processor exceeds a threshold. Upon that determination, a scheduler begins modify instruction issuance to one or more execution units until the power consumption is below the threshold. The modification of instruction issuance can be to slow instruction issuance or cease instruction issuance for a time period or until the power consumption is below the threshold.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the field of information or data processor architecture. More specifically, this invention relates to the field of implementing a computational or mathematical unit in a processor achieving power control via varying instruction issuance. 
       BACKGROUND 
       [0002]    Information or data processors are found in many contemporary electronic devices such as, for example, personal computers, personal digital assistants, game playing devices, video equipment and cellular phones. Processors used in today&#39;s most popular products are known as hardware as they comprise one or more integrated circuits. Processors execute software to implement various functions in any processor based device. Generally, software is written in a form known as source code that is compiled (by a complier) into object code. Object code within a processor is implemented to achieve a defined set of assembly language instructions that are executed by the processor using the processor&#39;s instruction set. An instruction set defines instructions that a processor can execute. Instructions include arithmetic instructions (e.g., add and subtract), logic instructions (e.g., AND, OR, and NOT instructions), and data instructions (e.g., move, input, output, load, and store instructions). As is known, computers with different architectures can share a common instruction set. For example, processors from different manufacturers may implement nearly identical versions of an instruction set (e.g., an x86 instruction set), but have substantially different architectural designs. 
         [0003]    Within a processor, numerical data is typically expressed using integer or floating-point representation. Mathematical computations within a processor are generally performed in computational units designed for maximum efficiency for each computation. Thus, it is common for a processor architecture to have an integer computational unit and a floating-point computational unit. As the use of graphic processing and scientific computing has expanded, the use of a processor&#39;s integer and floating-point mathematical capabilities has been increasing. Other factors, such as use for audio processing, are also contributing to an increased use of a processor&#39;s mathematical capabilities. To accommodate these and other needs, and to meet the ever growing demand for increased integer and floating-point performance, the computational capability of processors is continually evolving. 
         [0004]    When performing operations, including integer or floating-point computations, power virus code may occasionally cause the processor (or an operational unit) to consume more power than normal. Generally, power virus code comprises instructions that don&#39;t have any practical use; the code simply causes wasted power and operational cycles within the processor. Examples include code that causes unnecessary register-to-register data moves, operand reordering for commutative equations (e.g., addition or multiplication) or wait or no-op (no operation) instructions. In addition to wasting power and operational cycles, power virus code can cause the internal operating temperature of the processor to rise beyond specified performance parameters. Typically, an over-temperature condition causes a reset event to occur and the entire processor stops and is reset in accordance with a reset protocol. 
       BRIEF SUMMARY OF EMBODIMENTS OF THE INVENTION 
       [0005]    An apparatus is provided for modifying instruction issuance in a processor (or computational unit thereof) in response to power consumption exceeding a threshold. The apparatus comprises a decoder for decoding instructions to be performed and a power consumption monitor for determining when power consumption within the processor exceeds a threshold. Upon that determination, a scheduler begins modify instruction issuance to one or more execution units until the power consumption is below the threshold. The modification of instruction issuance can be to slow instruction issuance or cease instruction issuance for a time period or until the power consumption is below the threshold. 
         [0006]    In another embodiment, an apparatus is provided for modifying instruction issuance in a processor (or computational unit thereof) in response to power consumption exceeding a threshold for a particular instruction. The apparatus comprises a decoder for decoding instructions to be performed and providing a threshold to a power consumption monitor for that instruction. When the power consumption within the processor exceeds a threshold for the particular instruction, a scheduler begins modify issuance of the particular instruction to execution units until the power consumption is below the threshold. The modification of instruction issuance can be to slow issuance of the particular instruction or cease issuance of the particular instruction for a time period or until the power consumption is below the threshold. 
         [0007]    In yet another embodiment, an apparatus is provided for modifying instruction issuance in a processor (or computational unit thereof) in response to power consumption exceeding a threshold. The apparatus comprises a detector capable of determining that an energy event has occurred and a decoder for decoding instructions to be performed. A power consumption monitor determines when power consumption within the processor exceeds a threshold, which can be modified responsive to the detector identifying the occurrence of the energy event (for example, a battery powered device being “unplugged”). When power consumption exceeds the threshold, a scheduler begins modify instruction issuance to one or more execution units until the power consumption is below the threshold. The modification of instruction issuance can be to slow instruction issuance or cease instruction issuance for a time period or until the power consumption is below the threshold. 
         [0008]    A method is provided for controlling power consumption in a processor (or computational unit thereof). The method comprises monitoring power consumption in a processor (or computational unit) and determining that the power consumption of the processor (or computational unit) exceeds a threshold. Thereafter, instruction issuance if modified (such as by slowing or ceasing instruction issuance) within the processor (or computational unit) until the power consumption is below the threshold. 
         [0009]    In another embodiment, a method is provided for controlling power consumption in a processor (or computational unit thereof). The method comprises monitoring power consumption in a processor (or computational unit) and determining that the power consumption of the processor (or computational unit) exceeds a threshold. Thereafter, instruction issuance if modified (such as by slowing or ceasing instruction issuance) within the processor (or computational unit) until the power consumption is below the threshold. 
         [0010]    In yet another embodiment, a method is provided for controlling power consumption in a processor (or computational unit thereof). The method comprises monitoring power consumption in a processor (or computational unit) and determining that the power consumption of the processor (or computational unit) exceeds a threshold that varies upon detecting an occurrence of an energy changing event (such as a battery powered device being “unplugged”). Thereafter, instruction issuance if modified (such as by slowing or ceasing instruction issuance) within the processor (or computational unit) until the power consumption is below the threshold. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Embodiments of the present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and 
           [0012]      FIG. 1  is a simplified exemplary block diagram of processor suitable for use with the embodiments of the present disclosure; 
           [0013]      FIG. 2  is a simplified exemplary block diagram of floating-point unit or integer unit suitable for use with the processor of  FIG. 1 ; 
           [0014]      FIG. 3  is a flow diagram illustrating an embodiment of the present disclosure; and 
           [0015]      FIG. 4  is a flow diagram illustrating another embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Thus, any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Moreover, as used herein, the word “processor” encompasses any type of information or data processor, including, without limitation, Internet access processors, Intranet access processors, personal data processors, military data processors, financial data processors, navigational processors, voice processors, music processors, video processors or any multimedia processors. All of the embodiments described herein are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, the following detailed description or for any particular processor microarchitecture. 
         [0017]    Referring now to  FIG. 1 , a simplified exemplary block diagram is shown illustrating a processor  10  suitable for use with the embodiments of the present disclosure. In some embodiments, the processor  10  would be realized as a single core in a large-scale integrated circuit (LSIC). In other embodiments, the processor  10  could be one of a dual or multiple core LSIC to provide additional functionality in a single LSIC package. As is typical, processor  10  includes an input/output (I/O) section  12  and a memory section  14 . The memory  14  can be any type of suitable memory. This would include the various types of dynamic random access memory (DRAM) such as SDRAM, the various types of static RAM (SRAM), and the various types of non-volatile memory (PROM, EPROM, and flash). In certain embodiments, additional memory (not shown) “off chip” of the processor  10  can be accessed via the I/O section  12 . The processor  10  may also include a floating-point unit (FPU)  16  that performs the float-point computations of the processor  10  and an integer processing unit  18  for performing integer computations. Additionally, an encryption unit  20  and various other types of units (generally  22 ) as desired for any particular processor microarchitecture may be included. 
         [0018]    Referring now to  FIG. 2 , a simplified exemplary block diagram of a computational unit suitable for use with the processor  10 . In one embodiment,  FIG. 2  could operate as the floating-point unit  16 , while in other embodiments  FIG. 2  could illustrate the integer unit  18 . 
         [0019]    In operation, the decode unit  24  decodes the incoming operation-codes (opcodes) dispatched (or fetched by) a computational unit. The decode unit  24  is responsible for the general decoding of instructions (e.g., x86 instructions and extensions thereof) and how the delivered opcodes may change from the instruction. The decode unit  24  will also pass on physical register numbers (PRNs) from an available list of PRNs (often referred to as the Free List (FL)) to the rename unit  26 . 
         [0020]    The rename unit  26  maps logical register numbers (LRNs) to the physical register numbers (PRNs) prior to scheduling and execution. According to various embodiments of the present disclosure, the rename unit  26  can be utilized to rename or remap logical registers in a manner that eliminates the need to actually store known data values in a physical register. This saves operational cycles and power, as well as decrease latency. 
         [0021]    The scheduler  28  contains a scheduler queue and associated issue logic. As its name implies, the scheduler  28  is responsible for determining which opcodes are passed to execution units and in what order. In one embodiment, the scheduler  28  accepts renamed opcodes from rename unit  26  and stores them in the scheduler  28  until they are eligible to be selected by the scheduler to issue to one of the execution pipes. 
         [0022]    The execute unit(s)  30  may be embodied as any generation purpose or specialized execution architecture as desired for a particular processor. In one embodiment the execution unit may be realized as a single instruction multiple data (SIMD) arithmetic logic unit (ALU). In other embodiments, dual or multiple SIMD ALUs could be employed for super-scalar and/or multi-threaded embodiments, which operate to produce results and any exception bits generated during execution. 
         [0023]    In one embodiment, after an opcode has been executed, the instruction can be retired so that the state of the floating-point unit  16  or integer unit  18  can be updated with a self-consistent, non-speculative architected state consistent with the serial execution of the program. The retire unit  32  maintains an in-order list of all opcodes in process in the floating-point unit  16  (or integer unit  18  as the case may be) that have passed the rename  26  stage and have not yet been committed by to the architectural state. The retire unit  32  is responsible for committing all the floating-point unit  16  or integer unit  18  architectural states upon retirement of an opcode. 
         [0024]    Referring now to  FIG. 3 , a flow diagram is shown illustrating the steps followed by an embodiment of the present disclosure for the processor  10 , the floating-point unit  16 , the integer unit  18  or any other unit  22  of the processor  10 . The method begins in step  50  where power consumption of the processor (or any operational unit thereof) is monitored. In one embodiment of the present disclosure, average power is monitored over several operational cycles, for example, in a sigma-delta based accumulator. In other embodiments, an instantaneous power measurement could be used. In still other embodiments power consumption by instruction (or instruction type) could be stored in a table providing an expected power consumption for an instruction when it is decoded (for example, in decoder  24  of  FIG. 2 ). 
         [0025]    Next, decision  56  compares the measured or monitored power consumption to a threshold. In one embodiment of the present disclosure, the threshold is a fixed value that is set according to a thermal design point or other parameters of the processor (or operational unit). For example, the threshold could be set to just above the highest power for a known “real” opcode and defining any greater power consumption as a “power virus”. In other embodiments, the threshold is variable upon detection of an occurrence or event (see  FIG. 4  below). In still other embodiments, the threshold varies by instruction (or instruction type) responsive to an expected power consumption following decoding of an instruction. In any embodiment, one object of the present disclosure is to avoid overheating the processor or putting too much load on the power supply. 
         [0026]    If the determination of decision  56  is that the monitored power consumption is above the threshold, step  58  begins to modify instruction issuance to the execution units. In one embodiment, the scheduler ( 28  of  FIG. 2 ) slows release of instructions to the execution units ( 30  in  FIG. 2 ) thereby reducing power consumption. In other cases, the scheduler may cease issuing instructions for a time period or until the monitored power consumption returns to a level below the threshold (as determined by decision  56 ). In still other embodiments, the scheduler may slow or stop issuance of particular instructions determined to be wasteful of power upon execution. In any event, the present disclosure contemplates that power consumption may be controlled in the processor (or any operational unit thereof) by modifying instruction release to execution units to reduce power consumption or to maintain power consumption within certain operational parameters. 
         [0027]    Conversely, if the determination of decision  56  is that the monitored power consumption is not above the threshold, does not modify instruction issuance (step  60 ) and the method returns to step  50  and the process repeats. 
         [0028]    Referring now to  FIG. 4 , a flow diagram is shown illustrating the steps followed by another embodiment of the present disclosure for the processor  10 , the floating-point unit  16 , the integer unit  18  or any other unit  22  of the processor  10 . As with  FIG. 3 , the method begins in step  50  where power consumption of the processor (or any operational unit thereof) is monitored. In one embodiment of the present disclosure, average power is monitored over several operational cycles, for example, in a sigma-delta based accumulator. In other embodiments, an instantaneous power measurement could be used. In still other embodiments power consumption by instruction (or instruction type) could be stored in a table providing an expected power consumption for an instruction when it is decoded (for example, in decoder  24  of  FIG. 2 ). 
         [0029]    The method proceeds to decision  52  where it is determined whether a threshold changing event has occurred. According to the present disclosure, a threshold changing event comprises some change indicating that the threshold should be increased or reduced for power consumption purposes. For example, a laptop computer (such as shown in  FIG. 5A ), may operate from line current or from an internal battery. While “plugged in”, one threshold may be set to allow more instructions to be issued than when, for example, it is detected that the device has been “un-plugged” and is operating on battery power. Upon detection of such an event (decision  52 ), the threshold could be reduced (step  54 ), thus slowing the issuance of instructions (from scheduler  28  in  FIG. 2 ) to execution units ( 30  in  FIG. 2 ) to conserve power consumption. When returned to a line current source, the threshold could be returned or adjust to the former threshold level (again step  54 ). 
         [0030]    Conversely, if the determination of decision  52  is that a threshold changing event has not occurred, the method proceeds to decision  56 , which compares the measured or monitored power consumption to a threshold (which may or may not have been modified in step  54 ). If the determination of decision  56  is that the monitored power consumption is not above the threshold, instruction issuance is not modified (step  60 ) and the routine begins again at step  50 . 
         [0031]    Conversely, if the determination of decision  56  is that the monitored power consumption is above the threshold, step  58  begins to modify instruction issuance to the execution units. In one embodiment, the scheduler ( 28  of  FIG. 2 ) slows release of instructions to the execution units ( 30  in  FIG. 2 ) thereby reducing power consumption. In other cases, the scheduler may cease issuing instructions for a time period or until the monitored power consumption returns to a level below the threshold (via looping back through the routine of  FIG. 4 ). In still other embodiments, the scheduler may slow or stop issuance of particular instructions determined to be wasteful of power upon execution. In any event, the present disclosure contemplates that power consumption may be controlled in the processor (or any operational unit thereof) by modifying instruction release to execution units to reduce power consumption or to maintain power consumption within certain operational parameters. 
         [0032]    Various processor-based devices that may advantageously use the processor (or any computational unit) of the present disclosure include, but are not limited to, laptop computers, digital books or readers, printers, scanners, standard or high-definition televisions or monitors and standard or high-definition set-top boxes for satellite or cable programming reception. In each example, any other circuitry necessary for the implementation of the processor-based device would be added by the respective manufacturer. The above listing of processor-based devices is merely exemplary and not intended to be a limitation on the number or types of processor-based devices that may advantageously use the processor (or any computational) unit of the present disclosure. 
         [0033]    While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.