WinHEC2007_Designing Power-Friendly Devices

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This paper focuses on a generally-observed industry problem, where the behavior of devices causes a significant increase to system power. Much work has been done in Microsoft® Windows® operating systems such as Windows XP and Windows Vista™, as well as in the hardware on modern processors, chipsets, and supporting logic to enable deep processor and platform power management. Unfortunately, today’s systems are not optimized for situations where devices may generate power-unfriendly traffic patterns or do not support (or do not properly implement) baseline mobile platform features such as link power management or intelligent traffic management.
The first section of this paper covers key concepts of modern-day multicore platform power management works, with real-world data to illustrate the power impact of ill-behaved devices on platforms.
The second section focuses on PCI Express Base Specification 2.0 (PCIe) and some of the key challenges observed. This includes suboptimal usage of low-power link states and how certain traffic patterns may defeat important platform power management techniques. Key recommendations for PCIe devices including link state support, local power management policy, and production of activity patterns that help facilitate good platform energy efficiency.
) ?  a; c  ^# ZThe third section focuses on USB 2.0. It begins with an overview of the software model, traffic classes, and interface speeds, and then dives into device behavioral issues and recommendations including dynamic asynchronous scheduler management, conveying interrupt information through periodic endpoints, and the proper use of selective suspend.
This information applies for the following operating systems:
        Windows Server® Code Name “Longhorn”
( _4 K: w; x% M0 Q' m        Windows Vista
        Microsoft Windows Server 2003
; \9 M7 P3 [  b/ v  z        Microsoft Windows XP
1 _2 p& e/ b* P0 z, ?        Microsoft Windows 2000