HPET SPECIFICATION PDF
Software Developers Hpet Spec 1 0a – Download as PDF File .pdf), Text File .txt ) or read online. Updated HPET web link, added WSPT and WDAT, updated WDRT description and web link. Clarified that the endian-ness of data value. High Precision Event Timer Driver for Linux The High Precision Event Timer ( HPET) hardware follows a specification by Intel and Microsoft, revision 1.
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Save minimal tick either from ACPI table or configuration register. Otherwise it has no effect. A few options to use Traits were specificatuon as described in the next section, but we end up choosing the simpler approach due to the following reasons:.
High Precision Event Timer
It can also be a nuisance that the ever-increasing processor speeds of newer processor designs make specifixation usable time span shorter still.
Implementations have been observed in which the period register is off by parts per million or more. HPET is meant to supplement and replace the programmable interval timer and the RTC’s periodic interrupt function.
The following operating systems are known not to be able to use HPET: The following table skips reserved registers defined in the specification.
But we’ve also set bit 6. About This site Joining Editing help Recent changes. If 32 bit reads are performed on 64 bit counter, consult 2.
It was developed jointly by Intel and Microsoft and has been incorporated in PC chipsets since circa You can help by adding to it.
Otherwise, this bit will be ignored and reading it will always return 0. More information on this is provided further in the article.
The functionality is dependent of whether edge or level-triggered mode is used for timer n. Spceification page has been accessed 35, times. Common Devices Interrupts Time.
The difficulties are exacerbated if the comparator value is not synchronized with the timer immediately, but delayed by one or two ticks, as some chipsets do. Comparators are NOT required to support this mode; you must detect this capability when apecification a comparator.
Comparators can be driven by the operating system, e.
If it’s not, please analyze the meaning of specific fields in registers used above. Setting this bit to 1 enables triggering of interrupts. Timer n Interrupt Routing Capability. But this device has no driver and is not used at all. Reads will return current value of the main counter.
This page is not meant as a full description of HPET, only as a lightweight introduction. It is recommended to use 32 bit counter when on bit only software. This article needs additional citations for verification. A popular value is If she forgets hw: These comparators are or bit-wide. In non-periodic mode, the OS programs spexification of timer’s comparator registers with value of main counter that is to h;et an interrupt.
High Precision Event Timer – Wikipedia
This page was last edited on 24 Septemberspecificaion While and RTC can be put into an HPET-like one-shot mode, the set-up process is so slow that their one-shot mode is not used in practice for tasks requiring precise scheduling.
I believe that the wording could’ve been much better.
Work around hardware stupidity Archived at Archive. Webarchive template archiveis links Articles needing additional references from February All articles needing additional references Articles to be expanded from February All articles to be expanded Articles using small message boxes All articles with unsourced statements Articles with unsourced statements from December I hope the above code is obvious. End users can indicate their desire to have HPET in the guest by uploading their own images with the same trait.