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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Reads will return current value of the main counter. This section needs expansion with: From Wikipedia, the free encyclopedia.

Otherwise, this bit will be ignored and reading it will always return 0. This page was last modified on 31 Octoberat HPET is a continuously running timer that counts upward, not a one-shot device that counts down to zero, causes one interrupt and then stops.

There are two techniques to deal with this problem; they will both be described in later part of the article. 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 Example Spec – The title of your blueprint.


In one-shot mode the comparator fires an interrupt once when the main counter reaches the value stored in the comparator’s register, while in the periodic mode the interrupts are generated at specified intervals. This page has been accessed 35, times.

High Precision Event Timer

Each comparator can generate spwcification interrupt when the least significant bits are equal to the corresponding bits of the bit main counter value.

Update User Documentation for image properties [2]. This field is used to allow software to directly set periodic timer’s accumulator. Timer n Interrupt Routing Capability.

I believe that the wording could’ve been much better. A benchmark in that environment for 10 million event counts found that TSC took about 0. Compared to these older timer circuits, the HPET has higher frequency and wider bit counters although they can be driven in bit mode.

Enter search terms or a module, class or function name. Determine allowed interrupt routing for current timer and allocate an interrupt for it. Periodic mode is more tricky than non-periodic mode. This is a consequence of HPET’s main counter being up-counting.

If it’s not, please analyze the meaning of specific fields in registers used above.

HPET – OSDev Wiki

Besides mentioning the race condition discussed above, a VMware document also lists some other drawbacks: Writes of 0 have no effect. If you need any information not covered by this article, consult the HPET specification. For periodic mode, similarly to one-shot mode, you write a value at which an specofication shall be generated to the comparator register.


Views Read Edit View history. It was developed jointly by Intel and Microsoft and has been incorporated in PC chipsets since circa Namely, you probably want specifiation use some of ISA interrupts – or, at very least, be able to use them at one point unambiguously.

If she forgets hw: The following operating systems are known not to be able to use HPET: Setting this bit to 1 enables triggering of interrupts. It is recommended to use 32 bit counter when on bit only software. If 32 bit reads are performed on 64 bit counter, consult 2. HPET is meant to supplement and replace the programmable interval timer and the Npet periodic interrupt function.

Support High Precision Event Timer (HPET) on x86 guests — Nova Specs documentation

But this device has no driver and is not used at all. In non-periodic mode, the OS programs one of timer’s comparator registers with value of main counter that is to trigger an interrupt. Retrieved from ” https: