News

Windows 8 Designed To Limit Power Loss From Apps

• By Kurt Mackie
• 02/09/2012

Microsoft explained a bit more about the power-saving capabilities of Windows 8 and how that works with applications.

Most of the details had been summarized before by Microsoft during its Build developer conference in September, when the Windows 8 developer preview was unveiled. The basic idea is that background apps get suspended by the operating system to conserve battery life, which is especially useful for mobile device users. Lead program managers at Microsoft, Sharif Farag and Ben Srour, expounded on that concept in a "building Windows 8" blog post on Tuesday.

Perhaps the most interesting tidbit explained in the post is that Windows 8, when released as a product, will let the user close an application via touch, keyboard or mouse. This point, seemingly trivial, likely will be a tremendous relief for those who tried the Windows 8 developer preview tablets in September, which required the user to go find the Task Manager and kill an application in order to close it.

Still, Farag and Srour make a strong case for not closing apps at all when using Windows 8. Apps that a user isn't directly using will get suspended by Windows 8, and while those suspended apps consume some system memory, they draw no power, so there is no battery drain from them "running."

Microsoft makes a few exceptions to this power-saving scheme for background apps that play music, print, receive instant messages or e-mail or VoIP calls, synchronize or share content, download or upload files, or refresh "live tiles." If the apps running in the background are "Metro-style apps," they can perform those operations concurrently with an active app. Windows 8 comes with an application programming interface (API) that lets developers enable background processing for Metro-style apps, if needed. Another exception is antimalware applications, which may need to initiate a scan based on activity on the system.

Metro-style apps are written to take advantage of the new Windows Runtime environment introduced with the Windows 8 developer preview. They differ from so-called "desktop apps," or the classic menu-driven x86-based applications that are seen running on current Windows systems.

Microsoft typically claims that current (x86) applications capable of running on Windows 7 today will be able to run on Windows 8 when that OS is released. However, the claim neglects the nuance that Windows 8 is also being created to run on ARM-based silicon. It's likely that Windows 8 ARM devices won't support legacy x86 desktop apps, based on a comment made by Steven Sinofsky, president of the Windows and Windows Live Division. However, the x86 system-on-chip hardware being designed by AMD and Intel will support both legacy desktop apps and Metro-style apps. Microsoft announced the new system-on-chip support in January of last year.

Windows 8 running on the new system-on-chip technologies will enable a "connected standby" mode, which allows the device to receive communications (such as e-mail and instant messages) while conserving battery power, according to Farag and Srour. A new element in Windows 8, called the "desktop activity moderator," will control the resource use of applications that operate in this connected standby mode.

ARM chips being developed for Windows 8 are system-on-chip processors, too. Based on that fact, and the language in the blog post by Farag and Srour, veteran Microsoft watcher Mary Jo Foley hypothesizes that Windows 8 on ARM will support running classic desktop apps. However, even if that turns out to be the case, developers would have the task of recompiling their x86 apps to run on ARM-based metal, which likely would be a daunting prospect.

Consequently, those Windows 7 users with legacy x86 apps who are thinking that they want to run them on the new Windows 8 ARM platforms will be disappointed.