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Ralf Mardorf wrote:
> Pardon Rui
> Gustin and I are clueless because of HPET. Do you know any link? Or is
I know what an HPET is, I would to know what you mean by "HR Timer" and
A good primer on what an HPET is, what hardware and OSs support it, can
be found on
> there an understandable answer because of the hpet_max_user_freq issue?
I have no idea what this does.
> Gustin Johnson wrote:
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>> Ralf Mardorf wrote:
>>>>> I do know that MIDI jitter by Linux to equipment external the
>>>>> computer will decrease when using HR timer instead of System timer.
>>>>> I don't know the impact of the value for hpet_max_user_freq.
>>>> What is the difference?
>> To be more specific, define for me "System Timer" and "High Performance
>> Event Timer" (HPET) and how they are different.
>> Interestingly Windows XP does not support HPET even if the hardware is
>> equipped with it.
> AFAIK the system timer is using RTC and it's a programmable timer that
> interrupts the hardware periodically, while HPET won't interrupt the
> hardware in such a static way, because of the much higher resolution
> there will be less conflicts because of interrupts, dunno how this
> works. I guess to google for "tickless timer" might give some answers:
> http://www.google.de/#hl=de&ei=bJo2S7L5NdH5_Aar05iMCQ&sa=X&oi=spell&res num=0&ct=result&cd=1&ved=0CBoQBSgA&q=tickless+time r&spell=1&fp=6e1a413bb204dd20
> I didn't read the first link, but this one seems to be interesting and I
> guess I'll read it some day:
> Dunno if it's set up for my XP, but I once read a howto enable it for
> XP. It was just one short line to add somewhere. I guess you need
> service package 3.
> I searched, but I didn't found the link:
> http://www.google.de/#hl=de&q=HPET+XP+sp3&meta=&aq=f&oq=HPET+XP+sp3&fp= 6e1a413bb204dd20
> There's a discussion about this issue:
> Somewhere is a thread or Wiki about HPET on different OSs and IIRC there
> is described how to enable it for XP. But if it should be enabled, it's
> unclear if ASIO will use it.
>>> I can't remember if I used 64 or 1024 for hpet_max_user_freq, but
>>> IIRC on LAD there was the advice to build the kernel with using 64 by
>>> default, even if I should have used 1024, 64 might be the better value.
>> That does not seem like good advice if we are talking about the same
> A shot in the dark: The frequency always is 1,000,000,000 Hz for HPET
> timers, while the maximal frequency for system timers is 1,000 Hz. It
> might be that hpet_max_user_freq is a value how precise an interrupt has
> to be forced. If I guess correctly
, HR timers don't force it when
> there are no interrupts needed, while a normal timer always does this
> periodically. I can imagine that a value of 64 does mean, that there are
> some kind of ticks for the tickless system
, e.g. ... this might be
> complete nonsense ... 1,000,000,000/64=15625000, while
> 1,000,000,000/1024=976562.5 ... thus the higher value, will cause a less
> precise resolution for sync. I also have a theory the other way around
. We should ask this on LAD, instead of puzzling over this issue.
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