Abstract:
A system and method are provided for reducing power consumption within a video processing portion of a system. Activity associated within a video-processing portion of a personal digital assistant is analyzed. As reduced activity is identified, power conservation modes are implemented. In a normal mode of operation, a clock signal generated through an external oscillator is provided to a phase locked loop (PLL). An output clock signal from the PLL is then provided to several dividers to generate system clock signals. In a reduced mode of operation, the output clock from the external oscillator is provided to a divider, bypassing the PLL. Video processing components then use clock signals based on the external oscillator. In a suspend mode, both the PLL and the external oscillator are disabled.

Description:
PRIORITY APPLICATION 
   This patent application claims benefit under 35 U.S.C. 119(e) of the U.S. Provisional application No. 60/345,100 filed on Jan. 4, 2002, entitled: “SYSTEM FOR REDUCED POWER CONSUMPTION. 

   CO-PENDING APPLICATIONS 
   This application is related to U.S. patent application Ser. No. 10/083,875 entitled “SYSTEM FOR REDUCED POWER CONSUMPTION BY PHASE LOCKED LOOP AND METHOD THEREOF”, filed on Feb. 27, 2002, and U.S. patent application Ser. No. 10/083,917 entitled “SYSTEM FOR REDUCED POWER CONSUMPTION BY MONITORING VIDEO CONTENT AND METHOD THEREOF” filed on Feb. 27, 2002. 
   FIELD OF THE DISCLOSURE 
   The present invention relates generally to reducing system power consumption and more specifically to bypassing system components to reduce power consumption. 
   BACKGROUND 
   Handheld devices, such as personal digital assistants (PDA) and mobile phones, are now being equipped with hardware and software to handle several different computing tasks. Handheld devices are being equipped with communications adapters to allow the handheld devices to access the Internet, other handheld devices, and other information handling systems. Handheld devices are also being used to process multimedia data, such as audio and video data. Many handheld devices are capable of playing video on an integrated screen. Handheld devices are being integrated with more components to handle the increased functionality. However, as more components are integrated with the handheld devices and as processing increases, the handheld devices draw more power. 
   Power is limited on most handheld devices. Most desktop computers take power from a power supply connected to an alternating current (AC) power outlet and generally don&#39;t need to worry about conserving power. Handheld devices generally take their power from standard power cells. Handheld devices are designed to be small and light to make them portable for consumers. The power cells are generally selected to be small and light to not hinder the handheld device. However, the increased processing performed to handle new functionality, such as communications or multimedia playback, takes more power from the handheld devices than general processing tasks the handheld devices were originally used for. 
   Current methods of reducing power consumption are not adequate. To conserve power, a handheld device may reduce the speed at which its central processing unit (CPU) is run. However, inhibiting the CPU reduces the performance of the handheld device in most or all of the functions of the handheld device. Alternatively, specific functions or hardware components within the handheld device may be completely disabled to conserve power. However, completely disabling functions within the handheld device reduces a stability expected by a user. Power-saving modes can be enabled through software by having a software application decide processing can be reduced. However, such applications are not generally aware of the effect of running in a reduced power mode on other components within the device. The application may not be aware of all the processes running within the device. From the above discussion, it is apparent that an improved method of conserving power within a system would be useful. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Specific embodiments of the present disclosure are shown and described in the drawings presented herein. Various objects, advantages, features and characteristics of the present disclosure, as well as methods, operations and functions of related elements of structure, and the combination of parts and economies of manufacture, will become apparent upon consideration of the following description and claims with reference to the accompanying drawings, all of which form apart of this specification, and wherein: 
       FIG. 1  is a block diagram illustrating a system with provisions for conserving power, according to one embodiment of a present invention; 
       FIG. 2  is a flow diagram illustrating a method of identifying and initiating power conservation modes within a system, according to one embodiment of the present invention; 
       FIG. 3  is a block diagram illustrating a module for initiating power conservation modes within the system of  FIG. 1 , according to one embodiment of the present invention; 
       FIG. 4  is a block diagram illustrating a module for monitoring a number of instructions to be processed, according to one embodiment of the present invention; and 
       FIG. 5  is a block diagram illustrating a module for identifying changes in display content, according to one embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE FIGURES 
     FIGS. 1–5  illustrate methods of conserving power within a system. System properties are analyzed to initiate a power saving mode. A method of the present disclosure includes determining a power mode for a device. Modules within a system may be used to uniquely identify portions of the system that are capable of running in a reduced power mode. For example, a number of instructions in an instruction buffer can be analyzed to determine a level of power required to reliably process the instructions. A change in display content may be analyzed to determine the level of power required. When a lower than normal level of power is determined, the method includes disabling a phase locked loop used for generating a locked clock signal based on a raw clock signal from an external oscillator. The raw clock signal is used to drive a clock line for the system in place of the clock signal generated by the phase locked loop. When a normal level of power is determined, the method includes enabling the phase locked loop and providing the raw oscillator signal to an input of the phase locked loop. The locked clock signal is then provided from an output of the phase locked loop to the clock line. The present disclosure has the advantage of conserving power in a specific system component in response to operations associated with the component. 
   Referring now to  FIG. 1 , a block diagram illustrating a system with provisions for conserving power is shown, according to one embodiment of the present invention. In one embodiment of the present disclosure, system  100  handles video processing functions within a personal digital assistant (PDA) handheld device. A power module  300  initiates power conservation modes within system  100 . In one embodiment of the present disclosure, power module  300  monitors properties of system  100 , such as a fullness of instruction buffer  162  or changes in video content to be displayed. These system properties are used to determine a level of processing which is needed. When the properties of system  100  indicate a low or reduced level of processing is needed, power module  300  initiates power conservation modes. While system  100  is described in reference to a display data processing portion of a PDA, it should be appreciated that other forms of information handling systems or devices may be used. Furthermore, the methods and systems described herein would be useful to any such devices where power consumption is a concern. 
   An oscillator  110  is coupled to clock driver  115  to generate a raw clock signal for specific operations within system  100 . Oscillator  110  produces the raw clock signal at a fixed frequency. Higher frequencies operations may be desired than can be generated through oscillator  110 . Accordingly, a phase locked loop (PLL)  130  is used to generate a stable, locked clock signal from the raw clock signal generated by oscillator  110 . PLL  130  is generally used to generate multiplied clock signals based on the raw clock signal generated by oscillator  110 . It should be appreciated that oscillator  110  may include various oscillators. For example, various resistor/capacitor (RC) circuits or crystal oscillators may be used in place of oscillator  110  without departing from the scope of the present disclosure. 
   Several components of PLL  130  are used to generate a signal locked to the phase of the raw clock signal. The PLL  130  works as a control loop, attempting to correct for erratic changes in phase or frequency between the raw clock signal generated through oscillator  110  and a signal generated internal to the PLL  130 . In one embodiment, PLL  130  includes a phase comparator (not shown) to identify a difference in phase or frequency between the raw clock signal and the internal signal generated by PLL  130 . The comparator can include components or flops to generate a difference signal between the internal signal and the raw clock signal. The difference signal is provided to a filter (not shown), which generates a voltage signal associated with the difference signal. The voltage signal is provided to a voltage controlled oscillator (VCO, not shown) that generates an oscillating signal associated with the voltage signal. The oscillating signal is used as the internal signal mixed with the input raw clock signal. Accordingly, the oscillating signal may be output from the PLL  130  as a locked clock signal. 
   In one embodiment, the locked clock signal is coupled to a set of dividers  140  and  145 . In a normal operating mode, the set of dividers  140  and  145  generate clock signals based on the locked clock signal from PLL  130 . In one embodiment, the first divider  140  provides a first divided clock signal to the first clock bus  150 . The second divider  145  provides a second divided clock signal, with a lower frequency than the first divided clock signal, to the second clock bus  155 . The clock busses  150  and  155  may then be used to provide clock signals for various processing performed by system  100 . It should be appreciated that more or less clock busses can be used without departing from the scope of the present disclosure. 
   In one embodiment, a power module  300  initiates several power modes within system  100 . The power module  300  first identifies a processing status of system  300 . The status provides an indication of a level of activity, process or power consumption expected by system  100 . For example, power module  300  may monitor a number of instructions being stored in random access memory (RAM)  160 . Instructions to be processed are stored in an instruction buffer  162  of RAM  160 . RAM  160  can include various forms of memory, such as static dynamic random access memory (SDRAM) or dynamic random access memory (DRAM), without departing from the scope of the present disclosure. 
   Instruction buffer  162  includes a set of memory addresses of RAM  160  in a linked configuration. Instruction buffer  162  includes a write buffer  164  to identify a memory address within instruction buffer  162  where a new instruction is to be stored. A read pointer  165  identifies a memory address within instruction buffer  162  where the next instruction to be processed is read. As more instructions are pending, the number of linked memory addresses between write buffer  164  and read buffer  165  increases. In one embodiment, a threshold  166  is used to identify when the number of instructions pending in instruction buffer  162  has increased or decreased past a limit. It should be noted that the number of linked addresses within instruction buffer  162  can be fixed or dynamic. If the number of linked addresses within the instruction buffer  162  is fixed, the instruction buffer includes a set maximum number of pending instructions that can be supported. Accordingly, pending instructions may need to be dropped if a current number of pending instructions reached the maximum number of pending instructions. If the number of linked addresses within the instruction buffer is dynamic, memory addresses are dynamically allocated to instruction buffer  162  to meet a particular demand. While the size of the instruction buffer can increase as more instructions are received, there may not be enough time to adequately process all the instructions if the number of pending instructions is too high. 
   Furthermore, the types of instructions stored in instruction buffer  162  may be altered without departing from the scope of the present disclosure. In one embodiment, the types of instructions stored in instruction buffer  162  include display instructions for presenting video or graphics through display  195 . It should be appreciated that the instructions may include other instructions, such as multimedia processing instructions, such as video and/or audio processing commands. While instruction buffer  162  is shown as a part of RAM  160  and system  100 , it should be noted that instruction buffer  162  can be stored external to system  100 . 
   By monitoring the number of instructions in instruction buffer  162 , power module  300  may determine that an increased level of processing will be needed to process the number of pending instructions within a particular amount of time. For example, if a number of pending instructions is greater than a threshold  166 , or an increasing rate of the number of pending instructions is greater than a particular value, power module  300  initiates a normal, or high reliability, power mode, in which all or most power is available to system  100 . The normal power mode insures the instructions are processed using all available resources of system  100 . Alternatively, if read pointer  165  falls below threshold  166 , power module  300  may initiate a power conservation mode. Since the number of instructions to be processed is lower than normal, power module  300  can conserve excess power without overflowing the instruction buffer  162 . 
   In one embodiment, power module  300  monitors a rate of change of the number of instructions in instruction buffer  162 . If the number of instructions is increasing at a specific rate, power module  300  may switch from a power conservation mode to a normal power mode to anticipate an upcoming high demand for processing. Furthermore, power module  300  can be used to monitor the types of instructions stored in instruction buffer  162 . For example, instruction buffer  162  may store a number of instructions lower than threshold  166 ; however, the number of instructions can include process intensive instructions. Alternatively, the number of instructions may include simple instructions that can be processed quickly. Accordingly, power module  300  can initiate power conservation modes based on an amount of processing needed by the type of instructions stored in instruction buffer  162 . 
   Power module  300  can activate measures to respond to an identified power mode. When a normal power mode is initiated, power module  300  can provide power to all components of system  100 . For example, power module  300  can provide the raw clock signal generated by oscillator  110  to the input of PLL  130 . When a power conservation mode is initiated, power module  300  bypasses the locked clock signal output by PLL  130 . For example, in one embodiment, the locked clock signal output from the PLL  130  and the raw clock signal from the oscillator  110  are provided to a set of multiplexors  121  and  122 . In a normal mode of operation, multiplexers  121  and  122  provide the locked clock signal to clock busses  150  and  155 , respectively. When the power conservation mode is initiated, the power module  300  sets multiplexors  121  and  122  to only use the raw clock signal output by the oscillator  110 . Accordingly, during power conservation modes, the raw clock signal can be used as a clock source for dividers  140  and  145 . 
   The clock signal output by dividers  140  and  145  are provided to clock busses  150  and  155 , respectively, and used for processes within system  100 . While the raw clock signal generated by oscillator  110  may not be as fast or as stable as the locked clock signal generated through PLL  130 , the raw clock signal may be an adequate source for the second divider  145 , running at a slower speed than the first divider  140 . 
   To conserve power, power module  300  can also set the PLL  130  into a power down mode during the power conservation mode. In one embodiment PLL  130  is powered down by disabling clock signals input into the PLL  130 . A switch (not shown) can be provided to disable input of the raw clock signal generated through oscillator  110  to the PLL  130 . Alternatively, PLL  130  can be shut off by cutting power to the PLL  130 . However, it should be noted that as the PLL  130  may be a complementary metal oxide semiconductor (CMOS) device, it may be preferable to disable a clock signal provided to PLL  130  in place of disabling power provided to PLL  130 . 
   In one embodiment, power module  300  is capable of setting multiplexors  121  and  122  independently of each other. Accordingly, multiplexor  121  can be set to use the locked clock signal while multiplexor  122  is set to use the raw clock signal. Alternatively, a single multiplexor can be used in place of multiplexors  121  and  122  to provide either the locked clock signal or the raw clock signal to first divider  140  and/or second divider  145 . 
   In one embodiment, power module  300  monitors display content. For example, power module  300  monitors received display data, or compares a new set of display data to an old set of display data, to determine if the display content has changed. If the display content has not changed recently, power module  300  initiates a power conservation mode. If the display content has changed, the power module  300  may switch to, or remain in, the normal mode. 
   In one embodiment, when in a power conservation mode, power module  300  sends signals to enable power saving features through a display module  170 . In one embodiment, display module  170  controls a number of bits used to represent display data sent through display port  180 . To conserve power, display module  170  may be directed to use fewer bits to represent some or all bits of the display data. In on embodiment, a number of bits used to represent color is reduced. For example, the color depth of the display data can be reduced from 32-bit color to 16- or 8-bit color The display data is provided to a display device  195 , through display interface  190 . Display port  180  and display interface  190  use a set number of interface lines to transfer display data to display device  195 . In one embodiment, when fewer bits are used to represent the display data, less communications lines may need to be powered. Accordingly, less power is needed to transfer the display data from display port  180  to display device  195 , through display interface  190 . 
   The display interface  190  includes various interface adapters for transporting the display data to the display device  195 , such as a digital to analog converter (DAC), a transition minimized differential signaling (TMDS) transceiver, or a low voltage differential signaling (LVDS) transceiver, without departing from the scope of the present disclosure. While interface input lines can be disabled to reduce power, it should be appreciated that simply transmitting less data can conserve a substantial amount of power. Accordingly, a frame rate or a refresh rate associated with the display data being sent to display device  195  can be reduced to conserve power. As display content may not be changing, display module  170  can reduce the number of frames per second being displayed on display device  195  without drastically affecting the appearance of content displayed on the display device  195 . A bit depth used to represent other forms of multimedia data may also be reduced to lower power consumption. For example, a number of bits used to represent audio data may also be reduced to simplify multimedia processing and conserve power. Accordingly, power consumption can be reduced by having less data being transferred from display port  180  per unit time. In one embodiment, slower clock signals can be used to process multimedia data represented with a lower bit depth than multimedia data with a higher or normal bit-depth. In one embodiment, display device  195  includes a display device associated with a PDA, such as a liquid crystal display screen. 
   Power module  300  can initiate other forms of power conservation modes. In one embodiment, power module  300  initiates a suspend mode. Power module  300  can determine when system  100  has not been used for an extended period of time. If a lack of video data has been sent to system  100  or an information handling system interfaced with system  100  has not been active for a particular period of time, power module  300  initiates a suspend mode. Furthermore, if no instructions are provided to system  100 , power module  300  can initiate the suspend mode. In one embodiment, power module disables oscillator  110  as part of the suspend mode. Power module  300  may provide a signal to switch  125  to disable a signal provided from clock driver  115  to oscillator  110 . Alternatively, power module  300  may disable power to the clock driver  115  to disable oscillator  110  and the raw clock signal. Furthermore, power module  300  may provide a signal to display module  170  to disable display data output through display port  180 . 
   In one embodiment, power module  300  controls an amount of power provided to system  100 . Power module  300  may reduce a total amount of power provided to system  100  to match less power needed in power conservation modes, in comparison to a normal or nominal power mode. It should be appreciated that other forms of power conservation may also be incorporated without departing from the scope of the present disclosure. 
   Referring now to  FIG. 2 , a flow diagram illustrating a method of identifying and initiating power conservation modes within a subsystem of an information handling system is shown, according to one embodiment of the present invention. The subsystem, such as system  100  ( FIG. 1 ), may represent a portion of processing performed within the information handling system. For example, the subsystem may be used to handle video display for a portable information handling system, such as a PDA. A power module, such as power module  300  ( FIG. 1 ), monitors activity within the subsystem. When activity within the subsystem is reduced, the power module initiates a power conservation mode. 
   In step  205 , the power module sets the subsystem to a normal operating mode. In step  210 , in accordance with the normal operating mode, the power module enables an external oscillator, such as oscillator  100  ( FIG. 1 ), and a PLL, such as PLL  130  ( FIG. 1 ), associated with the subsystem. The power module may enable the external oscillator by providing power to a clock driver coupled to the external oscillator. The PLL may be enabled through a switch used to provide a clock signal generated by the external oscillator to the PLL. Alternatively, enabling the PLL can include enabling the output of the PLL to be provided to the subsystem. The power module may also allocate a normal or nominal amount of power to the subsystem and components within the subsystem. In one embodiment, the power module also enables the clock output from the PLL to be used by several components of the subsystem. 
   In step  220 , the power module monitors the status of components of the subsystem to identify a level of activity and an appropriate power mode. In one embodiment, the power module monitors a number of pending instructions to determine the power mode. For example, if the number of pending instructions has increased greater than a threshold, the power module may determine a normal, or high-reliability, power mode is necessary to ensure all the instructions are processed in time. Alternatively, if the number of pending instructions is less than the threshold, the power module may determine the subsystem may operate in a reduced operation mode, wherein power can be conserved. Furthermore, if no instructions are pending, the power module may determine that processing within the subsystem may be suspended by hardware components of the subsystem. 
   The power module may also monitor display content to determine a mode of operation or a power mode to employ. The power module may monitor the display content to determine if new content is to be displayed. If new display content is identified, the power module may determine a normal power mode is needed. If new display content is not different from old display content, the power module may determine the subsystem should be in a reduced operation mode to conserve power. 
   If a normal mode is to be used, the power module initiates a normal power mode in the device, such as previously discussed in reference to step  210 . Alternatively, if a reduced operation mode is to be used, the power module initiates a power conservation mode. Accordingly, in step  230 , the power module ensures the external oscillator is enabled. In step  240 , the PLL is bypassed. In one embodiment, the power module sets a switch or multiplexor to route a clock signal associated with the external oscillator to a clock divider coupled to the output of the PLL in the normal mode. The PLL can also be placed in a power down mode to conserve power while the PLL is bypassed and not being used. In one embodiment, the power module sets a PLL indicator to notify other portions of the subsystem that the PLL is disabled. A delay may need to be provided to allow particular portions of the subsystem time to switch to using the external oscillator for a clock source. Clock signals in the reduced operation mode may be divided to run processes slower than in the normal mode to account for a lack of stability associated with the clock signal generated by the external oscillator in comparison to a PLL output signal. Other forms of power conservation may also be employed in the reduced operation mode. For example, the power module may set the subsystem to represent display data with a reduced number of bits. Accordingly, a number of active interface input lines used to transmit display data to a display device, such as a PDA screen, may be reduced. A frame rate used to update video on a display device can also be reduced to conserve power. 
   If a suspend mode is to be used, the power module initiates a suspend mode in which several operations within the subsystem are disabled. Accordingly, in step  250 , the external oscillator is disabled. In one embodiment, a connection between the external oscillator and a clock driver is broken to disable the external oscillator. Furthermore, a driver signal generally provided to the external oscillator may be replaced with a ground signal. In one embodiment, steps are taken to place the subsystem into the reduced operation mode before initiating the suspend mode. The power module may provide a signal or set an indicator to notify other portions of the subsystem that a suspend mode will be initiated. It should be noted that hardware components may be necessary to transition out of a suspend mode. In one embodiment, the power module uses hardware components to monitor system properties to re-enabling subsystem functions when returning from the suspend mode. The hardware components may monitor user interface buttons. When a user has pressed a user interface button, the hardware components return from the suspend mode to a normal power mode. It should be appreciated that other modes of operation and other forms of conserving power can be employed without departing from the scope of the present invention. 
   Referring now to  FIG. 3 , a block diagram illustrating a module for initiating power conservation modes within the system of  FIG. 1  is shown, according to one embodiment of the present disclosure. A power module  300  monitors activity within a subsystem, such as system  100  ( FIG. 1 ). Dependent on operating characteristics associated with processes in the subsystem, such as a number of pending instructions or changes in display content, the power module  300  may initiate a power conservation mode. 
   Several components of power module  300  may be used to identify levels of activity within the subsystem. For example, an instruction-monitoring module  400  monitors a number of pending instructions. In one embodiment, instruction-monitoring module  400  compares the number of pending instructions to a threshold value. If the number of pending instructions is less than the threshold, power module  300  initiates a reduced operation, or reduced power, mode. Instruction-monitoring module  400  can also be used to monitor a rate of change in the number of pending instructions, as will be subsequently discussed in reference to  FIG. 4 . 
   A display-monitoring module  500  may be used to monitor operating characteristics associated with content to be displayed. Display-monitoring module  500  may notify power module  300  when display content has or has not changed. If the display content has not changed, the power module  300  may initiate a power conservation mode to make use of the lack of new display content. 
   Several controls within power module  300  can be used to initiate power conservation modes. For example, a clock control  340  can be used to apply controls to clocks used within the subsystem. For example, clock control  340  may be used to disable a PLL in a reduced operation mode. Clock registers of registers  310  may be set to indicate to other components of the subsystems that the PLL has been disabled. Clock control  340  may control a switch or multiplexor to route a clock signal generated by an external oscillator to dividers coupled with the disabled PLL. Clock control  340  may also notify other components to switch to the clock signal generated by the external oscillator in place of the clock signal output by the PLL in a normal mode. Furthermore, clock control  340  may be used to disable the external oscillator in a suspend mode in which most or all clocked operations in the subsystem are disabled. 
   A display control  350  can be used to reduce power associated with display elements in a reduced operation mode. In one embodiment, display control  350  is used to reduce a number of bits used to represent display data. For example, a color depth used to represent pixel elements may be changed. By reducing the number of bits used to represent display data, a number of communications or control lines activated to transfer video data from the subsystem to an interfaced display device or display screen can be reduced. By reducing the number of active interface lines, an amount of power needed to transfer the display data to the display device may be reduced. It should be appreciated that simply providing less data to the display device or display screen can substantially reduce power consumption. For example, a refresh rate associated with the display device or display screen can be reduced to conserve power. Furthermore, display data may be processed within the subsystem more quickly. A lower clock speed may be used to process the display data with the reduced number of bits. Accordingly, the display data may be reliably processed in a reduced operation/power mode. 
   A power control  320  can be used to control an amount of power provided to the subsystem. As a power conservation mode may be initiated, less power is needed by the subsystem. Power conservation techniques employed by the power module  300 , such as disabling the PLL or reducing the number of bits used to represent display data, reduce the total amount of power consumed by the subsystem. Accordingly, power control  320  may be used to reduce the total power provided to the subsystem. Power module  320  may reduce or disable power provided to particular components, such as the clock driver, in response to particular power conservation modes in place. 
   Registers  310  may be used to enable or disable particular power conservation modes or techniques. Registers  310  can also be used to indicate to other system components that a particular power mode is being implemented. Registers  310  also allow for several properties concerning transitions between power modes to be controlled. Table 1 provides a list of possible registers of registers  310  which may be used, according to one embodiment of the present disclosure. 
   
     
       
             
             
           
         
             
               TABLE 1 
             
             
                 
             
             
               REGISTER 
               DESCRIPTION 
             
             
                 
             
           
           
             
               POWER MANAGEMENT 
               ENABLES POWER MANAGEMENT 
             
             
               ENABLE 
               WITHIN THE POWER MODULE 
             
             
               CURRENT POWER MODE 
               STORED AN IDENTIFIER FOR THE 
             
             
                 
               CURRENT POWER CONSERVATION 
             
             
                 
               MODE 
             
             
               POWER MODE REQUEST 
               SOFTWARE TRANSITION BETWEEN 
             
             
                 
               POWER CONSERVATION MODES 
             
             
                 
               IF DIFFERENT FROM 
             
             
                 
               CURRENT 
             
             
               NORMAL/SLOW 
               ENABLES HARDWARE CONTROL 
             
             
               HARDWARE ENABLE 
               FOR TRANSITIONING FROM A 
             
             
                 
               NORMAL MODE AND A POWER 
             
             
                 
               CONSERVATION MODE 
             
             
               NORMAL-SLOW 
               DEFINES CONDITIONS 
             
             
               CONDITIONS 
               FOR HARDWARE TO TRANSITION 
             
             
                 
               FROM A NORMAL MODE TO 
             
             
                 
               A REDUCED 
             
             
               SLOW-NORMAL 
               ENABLES HARDWARE CONTROL 
             
             
               HARDWARE ENABLE 
               FOR TRANSITIONING FROM A 
             
             
                 
               REDUCED OPERATIONS MODE 
             
             
                 
               TO A NORMAL 
             
             
               SLOW-NORMAL 
               DEFINES CONDITIONS FOR 
             
             
               CONDITIONS 
               TRANSITIONING FROM A 
             
             
                 
               REDUCED OPERATIONS MODE 
             
             
                 
               TO A NORMAL MODE 
             
             
               WAKEUP CONDITIONS 
               DEFINES CONDITIONS HARDWARE 
             
             
                 
               USES FOR WAKING FROM 
             
             
                 
               A SUSPEND MODE 
             
             
                 
             
           
        
       
     
   
   Registers of register  310  can be used by components external to power module  300  to enable particular power conservation modes. A power management enable register can be used to enable or disable operation of the power module  300 . If power module  300  is disabled, the system may be set to run in only the normal power mode. Accordingly, user preferences may be linked to disable power conservation modes through the power management enable register. Registers  310  can also include a current power mode register that defines the current or active mode. A power mode request register can be used to force the power module  300  into a new power mode. Conditions for transitioning between power modes may also be set through registers  310 . For example, a wakeup condition register may be used to indicate different triggers to monitor for returning from a suspended operation mode. For example, the wakeup condition register may indicate the power module  300  should only leave a suspend mode when a power button or switch is activated by the user. 
   Referring now to  FIG. 4 , a block diagram illustrating a module for monitoring a number of instructions to be processed is shown, according to one embodiment of the present invention. Instruction-monitoring module  400  monitors a number of instructions pending. Instruction monitor module  400  provides analysis on pending instructions to a module capable of transitioning among power conservation modes, such as power module  300  ( FIG. 3 ). 
   A fullness monitor  410  tracks a fullness of an instruction buffer, such as instruction buffer  162  ( FIG. 1 ). New instructions to be processed are stored in memory, such as in instruction buffer  162 . Once a system, such as system  100  ( FIG. 1 ), is ready to process a new instruction, the instruction is read and removed, or de-allocated, from the instruction buffer. Dependent on a current level of activity in the system, the instruction buffer may fill with new pending instructions faster than old instructions are read. A threshold  415  may be used to compare a current number of pending instructions to a level of activity. In one embodiment, as the number of pending instructions increases greater than the threshold, the level of activity is considered high and may be reported as high through output registers  430 . Accordingly, the power module may use the reported level of activity to determine the system should be in a normal power mode, wherein all clocks and system components are allowed to operate. 
   Alternatively, the number of pending instructions may be equal to or less than the threshold  415 . The fullness monitor  410  provides an indicator through output registers  430  that the level of activity is low. The power module can use the reported level of activity to initiate a reduced operation mode in which power to some components is disabled. Furthermore, slower clocks signals can be used to conserve power. 
   A rate of change monitor  420  is used to monitor a rate of change in the number of pending instructions in the instruction buffer. The rate of change monitor  420  may calculate the rate of change in the number of pending instructions tracked through fullness monitor  410 . If the number of pending instructions increases at a high rate, the rate of change monitor  420  may provide a warning of increased activity to the power module, through output registers  430 . The power module may use the warning to switch from a reduced operations mode to a normal mode. Accordingly, the rate of change monitor  420  allows the power module to anticipate and react to the changes in the level of activity. In one embodiment, the fullness monitor  410  and rate of change monitor  420  include discrete components for monitoring the instruction buffer. For example, fullness monitor may include logic circuitry to toggle a flag on output registers  430  to indicate a particular power mode when a memory address being written to matches threshold  415 . In one embodiment, instruction-monitoring module  400  forms a part of a hardware subsystem to process display instructions associated with a PDA. 
   Instruction-monitoring module  400  can also include a content monitor  425 . Content monitor  425  monitors the types of instructions stored in the instruction buffer to anticipate an amount of processing that may be needed to process the instructions. Content monitor  425  can provide set an indicator through output registers  430  based on a level of processing intensity associated with the instructions stored in the instruction buffer. A first indicator can be used to indicate at least a majority of the instructions in the instruction buffer require minor processing and a second indicator can be used to indicate intensive processing is needed to process the instructions in the instruction bugger. Furthermore, the content monitor  425  can provide a number of instructions of a first type, requiring minor processing, and a number of instructions of a second type, requiring intensive processing. Accordingly, the power module can determine whether or not to enter a power conservation mode based on the types of instructions to be processed. 
   Referring now to  FIG. 5 , a block diagram illustrating a module for identifying changes in display content is shown, according to one embodiment of the present invention. A display-monitoring module  500  is used to analyze display activity. Display-monitoring module  500  analyzes display activity to provide a power module, such as power module  300  ( FIG. 3 ), to ascertain a level of activity associated with a system, such as system  100  ( FIG. 1 ). 
   In one embodiment, to determine when changes in display content have occurred, display-monitoring module  500  analyzes different sets of display content. A first set of display content  510  may include a set of display data currently being displayed. A second set of display content  520  may include a set of display data that will be displayed. A content analyzer  530  compares the display data of the two sets of display content  510  and  520 . If the sets of display content  510  and  520  are substantially different, content analyzer can set a flag of output registers  530  indicating the display content is changing. Alternatively, if the two sets of display content  510  and  520  are substantially the same, the content analyzer  530  may apply a value to a register of output registers  530  indicating the display content is not changing. The sets of display content  510  and  520  may include portions of the total display content, allowing content analyzer  530  to determine how much of the display content is actually changing. If only a few portions of the total display content change, the content analyzer may not consider the sets of display content  510  and  520  substantially different. In one embodiment, the sets of display content  510  and  520  are stored in memory, such as in video memory or a frame buffer. 
   In one embodiment, the power module monitors output registers  530  to determine display activity. If the display content appears to be changing, the power module may initiate a normal power mode to ensure the new display data is processed in time. Alternatively, if the display content is not substantially changing, the power module may initiate power conservation modes. In one embodiment, the power module reduces the number of bits used to represent display data. Using the reduced number of bits, the display data may be processed at slower speeds and less active communications lines are needed to provide the display data to a display device or screen. Furthermore, a frame rate used to output display data can also be reduced. Accordingly, by reducing an amount of data output through a display port, power consumption associated with display data processing and display can be reduced. In one embodiment, the display-monitoring module  500  is part of a set of hardware components used to process display content for output through a display device. While display content is discussed in reference to display-monitoring module  500 , it should be appreciated that other forms of content may also be monitored without departing from the scope of the present invention. For example, audio content to be output may be monitored to determine a power mode to be initiated. 
   The systems described herein may be part of an information handling system. The term “information handling system” refers to any system that is capable of processing information or transferring information from one source to another. An information handling system may be a single device, such as a computer, a personal digital assistant (PDA), a hand held computing device, a cable set-top box, an Internet capable device, such as a cellular phone, and the like. Alternatively, an information handling system may refer to a collection of such devices. It should be appreciated that the system described herein has the advantage of dynamically reducing power consumption in response to system activity. 
   In the preceding detailed description of the embodiments, reference has been made to the accompanying drawings which form a part thereof, and in which is shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the spirit or scope of the disclosure. To avoid detail not necessary to enable those skilled in the art to practice the disclosure, the description may omit certain information known to those skilled in the art. Furthermore, many other varied embodiments that incorporate the teachings of the disclosure may be easily constructed by those skilled in the art. Accordingly, the present disclosure is not intended to be limited to the specific form set forth herein, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents, as can be reasonably included within the spirit and scope of the disclosure. The preceding detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present disclosure is defined only by the appended claims.