Since the original specification for HPET in calls for a high resolution counter, which is then exposed by the QueryPerformanceFrequency and QueryPerformanceCounter API calls already available since Windows , it is the QueryPerformanceFrequency that can shed light on how this “high precision” counter is actually being provided. Newer operating systems tend to be able to use either. Sign up using Email and Password. 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. So the HPET is only there to satisfy the system’s high speed needs. A benchmark in that environment for 10 million event counts found that TSC took about 0. Please help improve this article by adding citations to reliable sources.
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High Precision Event Timer
The difficulties are exacerbated if the comparator value is not synchronized with the timer immediately, but lihux by one or two ticks, as some chipsets do. 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.
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This causes an interrupt at every millisecond even if the application needs to do actual work less frequently. Work around hardware stupidity Archived at Archive. From Wikipedia, the free encyclopedia. February Learn how and when to remove this template message. Some hardware has both. Email Required, but never shown. 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.
Will the computer have better entropy with HPET? Compared to these older timer circuits, the HPET has higher frequency and wider bit counters although they can be driven in bit mode. Performance is not a problem, I would like a good entropy, and cryptographically secure random numbers. Besides mentioning the race condition discussed above, a VMware document also lists some other drawbacks: Each comparator can generate an interrupt when the least significant bits are equal to the corresponding bits of the bit main counter value.
cryptography – HPET effects on CSPRNG for Linux OS – Information Security Stack Exchange
Implementations have been observed in which the period register is off by parts per million or more. Comparators can be driven by the operating system, e. A benchmark in that environment for 10 million event counts found that TSC took about 0. Since the original specification for HPET in calls for a high resolution counter, which is then exposed by the QueryPerformanceFrequency and QueryPerformanceCounter API calls already available since Hptit is the QueryPerformanceFrequency that can shed light on how this “high precision” counter is actually being provided.
Formerly referred to by Intel as linuc Multimedia Timer the term HPET was selected to avoid confusion with the multimedia timers as a software feature introduced in the MultiMedia Extensions to Windows 3.
HPET is meant to supplement and replace the programmable interval timer and the RTC’s periodic interrupt function.