Advanced Programmable Interrupt Controller: Difference between revisions

Revision as of 04:18, 17 January 2024

Revision as of 03:22, 16 July 2024

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Another advantage of the local APIC is that it also provides a high-resolution (on the order of one [[microsecond]] or better) timer that can be used in both interval and one-off mode.<ref name="timer">Uwe Walter, Vincent Oberle [http://telematics.tm.kit.edu/publications/Files/61/walter_ibm_linux_challenge.pdf μ-second precision timer support for the Linux kernel]</ref>

The APIC timer had its initial acceptance woes. A Microsoft document from 2002 (which advocated for the adoption of [[High Precision Event Timer]] instead) criticized the LAPIC timer for having "poor resolution" and stating that "the clocks silicon is sometimes very buggy".<ref>[{{Cite web |date=2002-09-20 |title=Guidelines For Providing Multimedia Timer Support |url=http://msdn.microsoft.com/en-us/library/windows/hardware/gg463347.aspx Guidelines|url-status=deviated For|archive-url=https://web.archive.org/web/20120728124718/http://msdn.microsoft.com/en-us/library/windows/hardware/gg463347.aspx Providing|archive-date=2012-07-28 Multimedia Timer Support], September 20, 2002|website=Microsoft}}</ref> Nevertheless, the APIC timer is used for example by [[Windows 7]] when [[Profiling (computer programming)|profiling]] is enabled, and by [[Windows 8]] in all circumstances. (Before Windows 8 claimed exclusive rights to this timer, it was also used by some programs like [[CPU-Z]].) Under Microsoft Windows the APIC timer is not a shareable resource.<ref>{{Cite web|url=https://social.msdn.microsoft.com/Forums/windowsdesktop/en-US/5d075378-a45f-433b-a3f7-73f974ec962f/windows-8-and-apic-timer?forum=wdk|archive-url=https://web.archive.org/web/20140222070735/http://social.msdn.microsoft.com/Forums/windowsdesktop/en-US/5d075378-a45f-433b-a3f7-73f974ec962f/windows-8-and-apic-timer?forum=wdk|url-status=dead|title=Windows 8 and APIC timer|archive-date=22 February 2014|website=social.msdn.microsoft.com|access-date=14 May 2023}}</ref>

The aperiodic interrupts offered by the APIC timer are used by the [[Linux kernel]] [[tickless kernel]]