Intel ATX Power Supply Design Guide: How Intel dual-core mobile platforms are affected by high clock-interrupt rates and sleep states.

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Introduction

How Intel® dual-core mobile platforms are affected by high clock-interrupt rates and sleep states.

By Karthik Krishnan, Intel Corp.

The Win32* interface provides various APIs for periodic execution of an application code at a desired frequency. These are based on the periodic timer ticks of the system clock built into the Hardware Abstraction Layer (HAL) of the Microsoft Windows* operating system. Various applications such as multimedia playback have threads for disk I/O, decoding, audio-video output and UI. Typically they use the timer based interrupts for periodic execution of a code section before or at a particular timeline (for example, play audio every 90 milliseconds, etc.) The following are the most commonly used APIs for this scenario:

timeSetEvent(UINT uDelay, UINT uResolution, LPTIMECALLBACK lpTimeProc, DWORD_PTR dwUser, UINT fuEvent)

This is a multimedia timer from Win32 that runs in its own thread that is available from winmm.lib. The callback function can be either executed periodically or scheduled once, depending on the fuEvent parameter.

SetTimer(HWND hWnd, UINT_PTR nIDEvent,UINT uElapse, TIMERPROC lpTimerFunc) available through user32.dll

The most common usage of this function is to post a WM_TIMER message periodically to an application window and invoke the callback while handling the timer message.

There are additional APIs such as WaitableTimers(), QueuedTimers(), etc.; however, all of them use the system clock to trigger timer-based code execution.