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The necessity to expand portability, performance and functionality in PCs and the need to squeeze every last microwatt from compact power sources are the primary drivers for software control of power management. Those musts are exemplified by the Advanced Configuration and Power Interface (ACPI), a system-level interface specification widely characterized as the first real effort to seamlessly merge software and hardware decision-making. "Software management is now viable for a wide range of applications, especially mobile PCs," said James Kardach, senior mobile platform architect for Intel's Mobile and Handheld Products Group (Santa Clara, Calif. ). "The 1992-1995 time frame was particularly right for development of this spec, as new marketability and end-user pull converged," he said, noting that after a decade of development, the capability of hardware management had reached its limit. "There's a whole new batch of applications for ACPI. While there are still some standardized [fixed] hardware functions, there's also generic hardware to provide abstraction layer interfacing to drivers through obj ect-oriented programming code. The next step will be to introduce some ACPI-compliant hardware alongside."
Implementation of this functional (as opposed to physical) interface specification is expected to affect a number of areas. They range from "OnNow" ( soft or instant on) applications for activation of PCs from their standby mode for receiving faxes, to battery control and monitoring in switching power supplies and uninterruptible power supplies. These applications include managing power in add-on boards such as printers, keyboards and sound cards. ACPI will also influence application to so-called self-ac and battery-powered devices as outlined in the IEEE 1394 Power Management specification.
"The devices must comply and so must the buses and the entire system," said Dave Dickens, 1394 product manager at Texas Instruments Inc., pointing out ACPI's place in the OnNow power initiative, the rest of which includes the operating system, bus-level protocols and devicelevel specifications. "Up until now, there's been no power management for the desktop, of which portable systems are seen the most," said Dickens, whose focus is primarily on PCI bus power management. "The power-management system must at least have a common framework."
The OnNow initiative, now embodied in a series of device-class specificationscommunications, displays, PC cards, storage, networking and the human interfacemakes the PC available for full service when...