Electrical computers and digital processing systems: support – Computer power control – Power conservation
Reexamination Certificate
2000-04-28
2003-02-18
Wong, Peter (Department: 2181)
Electrical computers and digital processing systems: support
Computer power control
Power conservation
C713S323000
Reexamination Certificate
active
06523125
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an information handling system typically represented by a personal computer and a method of controlling the same and, particularly, to an information handling system of a type which implements a low power consumption technology which causes the system to enter a state in which a task under execution is interrupted upon occurrence of a predetermined event with the operation of the system halted almost completely and a method of controlling such information handling system. More particularly, this invention relates to an information handling system of a type which shifts to a low power consumption mode after saving the system conditions in an external storage device such as a hard disk and restores the original operation mode by restoring the saved conditions and which is capable of saving the system conditions without destructing user data existing on the external storage device, and a method of controlling such information handling system.
BACKGROUND OF THE INVENTION
Along with recent technological revolution, various types of personal computers (PC) including a desk top type, a tower type and a notebook type have been developed and sold. Among them, the desk top PC is characterized in that the size is relatively large, the weight is relatively heavy and it is installed for use in a fixed place in an office or home. A notebook PC is designed and manufactured in a small size and a light weight in consideration of use in a mobile environment, that is, portable use in outdoor or a place where it is brought out. A typical example of a notebook PC is “IBM ThinkPad 770” series (trademark of International Business Machines Corporation) sold by IBM Japan Co., Ltd.
As well known, a notebook PC is of a “clam shell structure” comprising a system unit which internally installs a system board and a lid which is pivotally attached to a substantially rear edge of the unit (refer to FIG.
6
). A keyboard unit is disposed as an input device on the top surface of the system unit while a liquid crystal display is disposed as an output device substantially in the middle of the inside of the lid. When a notebook PC is used, the lid is opened from the system unit to allow the display and the keyboard to be usable. On the other hand, the lid is closed to the system unit when the notebook PC is not used or is transported to hide the display and the keyboard for protecting them from an external impact. The PC can install a hard disk drive (HDD), a floppy disk drive (FDD) and a CD-ROM drive as an external storage device. These drives are typically formed in a shape of a package so as to allow them to be attached, detached and exchanged at will.
Almost all PCs are of a “battery driven” type which can be driven by an internal battery. This is in consideration of a use in a mobile environment where a commercial power is not available. A battery internally installed in a notebook PC is generally in a form of a “battery pack” which contains a plurality of secondary battery cells such as Li-Ion, NiCd and NiMH cells. Such battery pack is typically of several hundreds grams of weight and has 4-12 volts output voltage.
The popularization and performance of a battery driven equipment depend on the effective utilization of a battery. Taking a battery pack of a notebook PC for example, it takes 2-3 hours to charge the pack despite the charged capacity is only enough to supply no more than 2-3 hours at most of computer processing time. Such a long charging time is a problem in using a battery driven equipment and this leads to a necessity for a user to have to carry a plurality of spare battery packs.
In view of the above, a technology of reducing power consumption has been researched and developed to extend the length of durable time of a battery as long as possible and have been employed in a battery driven equipment like a notebook PC.
Also, from a social ecological view point of limited resources, a demand for saving power consumption has been recently emphasized even for an electronic equipment which can be fed from a commercial power source unlimitedly. For example, the US Environment Protection Agency (EPA) publicized a self imposed regulation of saving power consumption called “Energy Star Computer Program” in June 1993. This regulation requires that the power consumption of a PC in a stand-by state is below a given criteria (driving power is no more than 30 watts or 30% of a power in operation of a PC). From this reason, computer manufacturers have been competing in implementing a power save technology even in a desk top PC.
Among the various technologies of reducing power consumption for electronic equipments, one applied to a PC may be called “power management”.
The principal mechanism of the power management is to put a hardware which need not be driven to a power save mode or to stop feeding depending on the activity of a computer system (hereinafter may be simply referred to a “system”). Example of the power management includes “LCD off”, “HDD off” and “CPU slow clock/clock down”.
“LCD off” stops feeding an LCD or a back light thereof in the absence of an input from the keyboard or a mouse over more than a predetermined length of time. “HDD off” stops feeding circuits inside a HDD unit depending on the length of time measured from the latest disk access and is described in the specification of U.S. Pat. No. 4,933,785, for example. Because the back light of LCD and a drive motor of HDD occupy a large percentage of the total power consumption of a system, “LCD off” and “HDD off” contribute largely to power saving.
“CPU slow clock” and “CPU clock down” reduce the power consumption of the CPU by lowering the operating frequency of the CPU or stopping the clock completely during a stand-by time of the CPU (when there is no key/mouse input from a user over more than a predetermined length of time, for example). Because the processing capability of a CPU has been greatly enhanced while, on the other hand, the power consumption and heat generation of the CPU tend to increase due to the increasing speed of the CPU recently, “CPU slow clock/clock down” gives a significant technical merit. Incidentally, “CPU slow clock/clock down” is disclosed, for example, in the specification of Japanese patent application 7-278904 (PUPA 9-128106, Applicant Docket No. JA995100) assigned to the applicant of the present patent application.
The above described “LCD off”, “HDD off” and “CPU slow clock/clock down”, etc., reduce power consumption by halting a part of hardwares within the system while the rest of the hardwares continue to consume electric power. However, if feeding to the system can be almost completely stopped, it is needless to say that the effect of reduced power consumption will be further improved. In the case of chargeable battery, degradation of the battery may be induced if the battery continues to be discharged in a “low battery” condition in which the remaining capacity is below a predetermined value. It is therefore desirable to completely stop feeding to the system when the battery is in a low battery condition.
So called “hibernation” is a power management technology which enables feeding to the system to be completely stopped. The system is triggered to shift to a hibernation state by interrupting a task under execution when a key/mouse input or the activity of I/O device is not detected over more than a predetermined length of time or the battery is in a low battery state. Restoration of a system from the hibernation mode is called “wake up”. The “wake up” restores the system to an original state to resume the task and is distinguished from the usual power-on (POR: Power on Reset) which resets the state of the system.
In order to resume the task by wake up, that is, to restore the state of the system at the point of time when the task was interrupted, it is necessary to save the state of the system before it enters a hibernation mode. The state of the system as meant here in this specification includes information of the content of a volatile memory suc
Kohno Hiroshi
Shimotohno Susumu
Cameron Douglas W.
Dougherty Anne Vachon
Phan Raymond N
Wong Peter
LandOfFree
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