Electrical computers and digital processing systems: support – Computer power control – Power conservation
Reexamination Certificate
2001-02-14
2004-12-21
Browne, Lynne H. (Department: 2116)
Electrical computers and digital processing systems: support
Computer power control
Power conservation
C713S322000
Reexamination Certificate
active
06834354
ABSTRACT:
TECHNICAL FIELD
This invention relates to a reduction of power consumption of an information processing system, and more particularly to an information processing system and a control method therefor of the type in which the reduction in power is realized by suitably suppressing operation frequency of processor (CPU: Central Processing Unit) serving as core of data processing within the system. More specifically, this invention relates to an information processing system and a control method therefor in which the reduction in power is realized while maintaining a service quality of the system.
BACKGROUND ART
With the recent technical innovation, various personal computers (hereinafter referred to as “PC” or “system” as occasion may demand) such as the desk top type or note book type, etc., and/or work stations have been developed and come into the market. Among these equipments, personal computers of the note book type are designed and manufactured so that they are compact and light in weight by taking into consideration of portable/carriable use at the outdoor.
One feature of the note book type PC is of “battery driven type” which can be driven also by battery included therewithin. This enables use at the place where commercial power supply is not available. Battery that the note book PC includes therewithin generally takes a form of “Battery pack” in which plural chargeable type battery cells (hereinafter referred to as “secondary battery” as occasion may demand) utilizing lithium ion, etc. are connected and are packaged. While such battery pack can be re-utilized by charging, charge capacity per one operation is about two to three hours at the upmost when converted in point of operation time. In addition, charge time which is the same degree as the operation time is required. For this reason, for the purpose of elongating duration time of the battery any more, various devices for realizing reduction in power are made. It can be said that the fact that power saving function is positively introduced is also one of features of note book PCs.
In recent years, also with respect to desk top type PCs which can be inexhaustibly supplied with power by commercial power supply, from the viewpoint of ecology, power saving requirement is increased. The United States Environmental Protection Administration (EPA) has announced voluntary limitation called “Energy Star Computer program” in June, 1993 to require that power saving in the operation standby state is less than predetermined reference (drive power is less than 30 W, or less than 30% of that at the time of CPU full working). For this reason, every computer maker has made a research/development of computer products along this limitation plan.
A power saving of computer is realized by reducing, e.g., drive powers themselves of respective electric circuit components within the system. Moreover, such power saving is also realized by suitably lowering or interrupting power supply with respect to hardware components in which an operation state (activity) is lowered, or an unused state is continued. The power saving function as the latter may be also particularly called “Power Management”.
As mounting form of the power management in PC, there are mentioned power OFF of LCD (Liquid Crystal Display) and its back light and stop of disk rotation motor of Hard Disk Drive (HDD), etc. Since devices or the like such as LCD unit and/or HDD, etc. take great percentage with respect to total power consumption of the system, it can be said that an effect of power saving by LCD OFF and/or HDD OFF is extremely high.
Moreover, since CPU (Central Processing Unit) takes about one fourth (¼) of the total power consumption of the system, expectation with respect to power saving is high.
With respect to the liquid crystal display and bard disc unit, there has been already an outlook that power consumption is reduced. On the contrary, there is high possibility that the power consumption of CPU is further increased by high integration or realization of higher speed of operation frequency, etc. also in future. For this reason, it is deemed that an importance of power management with respect to CPU will be increased still more in future.
Typical method for realizing power management of CPU is realized by the suppression of operation frequency. Power consumption of the circuit component is determined by quantity of current passing through the transistor gate (i.e., resistor) per unit time. Namely, the power consumption is increased substantially in proportion to realization of high speed of operation frequency. Conversely, by dropping stepwise operation frequency in accordance with load state of CPU, quantity of current passing through the gate is suppressed and a reduction of the power consumption can be thus realized. By also lowering power supply voltage in accordance with drop of operation frequency, the power consumption can be further reduced.
It is to be noted that since lowering of operation frequency of CPU means lowering of performance of CPU, there exists the relationship of trade-off with respect to service quality (or degree of satisfaction of user who requests performance of the system).
For example, when CPU drivable by operation frequency above, e.g., 300 MHz continues full working at all times, battery capacity is dissipated in a short time, and all tasks do not always require full working of CPU. There exists a task in which sufficient service quality can be obtained also under operation mode of CPU which has been placed in clock down state. Alternatively, when the system is in user input standby state, there hardly exist bad influence or effect in the degree of satisfaction of user if the CPU is placed in clock down state.
On the other hand, when power management operation (i.e., clock down) of CPU is enabled during an execution of processing for which real time characteristic is required, lowering of service quality of the system is also invited as the result of the fact that performance is lowered.
In other words, real time task means processing in which there is necessity of completion before predetermined time limit (dead line), and there is mentioned, e.g., processing in which respective frames of MPEG (Moving Picture Expert Group)-compressed moving picture are reconstructed to carry out picture display, or the like. In this case, it is necessary to complete processing to MPEG-reconstruct one frame per one thirtieth sec., which is display time of frame to display it. Namely, processing of respective frames are carried out with one thirtieth sec., being as dead line, resulting in that dead line is not maintained. Thus, frames in which their processing cannot be completed before processing start of the next frame result in “frame missing” or “repetition” of frame. In general, applications including moving picture reproduction/synthesis or sound synthesis/recognition, etc. not only requires real time characteristic, but also applies heavy load to the CPU.
When power management is caused to take preference to lower performance of CPU during execution of such a real time processing, processing is not completed before deal line. Thus, the meaning that processing is continued is eliminated. In addition, when dead line is not kept, service quality of the system (i.e., degree of satisfaction of user) is lowered as the result of the fact that the frame missing or a repetition of frame takes place.
To summarize the above-mentioned facts, since power management of CPU means lowering of its performance, there results in trade-off relationship with respect to service quality of the system. Accordingly, it is preferable in view of optimization of the entirety of the system that power management of CPU is carried out within the range that the response time of the system permits.
DISCLOSURE OF THE INVENTION
An object of this invention is to provide an excellent information processing system and a control method therefor which are capable of realizing power-saving by suitably suppressing operation frequency of processor serving as the core of data p
Browne Lynne H.
Frommer Williams S.
Frommer & Lawrence & Haug LLP
Simon Darren M.
Sony Corporation
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