Even if it’s not (quite) winter yet, Apple is working on ways for your devices to “hibernate.” Patent number 8327171 has appeared at the U.S. Patent & Trademark Office for a method and apparatus for facilitating device hibernation.
One embodiment of the present invention provides a system that enables a computing device to save additional power by entering a “hibernation mode.” This seems to differ from “sleep mode.” The active state of the computing device is preserved in non-volatile storage while power to volatile storage is turned off.
During operation, the system reanimates a computing device from a hibernation image by restoring reanimation code from the hibernation image and then executing the reanimation code. While executing this reanimation code, the system restores the rest of the hibernation image by, reading compressed data containing the rest of the hibernation image, and decompressing the compressed data using computational circuitry within the computing device. During this process, the decompression operations are overlapped with the reading operations to improve performance.
Here’s Apple’s background on the invention: “Power conservation is critically important for many types of computer systems. For example, portable computer systems need to conserve power in order to operate for long periods of time on battery power. Power conservation is also important for desktop computer systems in order to meet the strict power-usage requirements for ENERGY STAR qualification.
Many computer systems save power by entering a power-saving state known as ‘sleep mode,’ when they are not busy. During sleep mode, power is saved by placing much of the computer system in a low-power state, while power is maintained to volatile memory. Maintaining power to volatile memory preserves the active state of the computer system and thereby facilitates a nearly instant wake-up process, which provides an excellent user experience.
“One drawback of existing sleep systems is that if power is lost during sleep mode, any unsaved work in volatile memory disappears. This loss of power can be easily triggered if a user is distracted for a few hours, or takes too long when performing a sleep-swap of the system battery. Unfortunately, as computer systems begin to incorporate larger amounts of random-access memory (RAM), correspondingly more power is required keep this RAM memory powered up during sleep mode. At the same time, as portable computer systems become progressively thinner and lighter, they contain correspondingly smaller batteries.
As a consequence of these trends, a few years ago, a laptop computer system could be expected to last multiple days in sleep mode, whereas at present, a new laptop computer system can rarely last more than a full day in sleep mode when it is configured with a maximum amount of RAM. Hence, what is needed is a method and an apparatus that enables computer systems to save additional power beyond what can be saved by entering sleep mode.”
The inventors are Dean Reece and Simon M. Douglas.