Another look at HPET High Precision Event Timer

Discussion in 'Videocards - NVIDIA GeForce Drivers Section' started by Bukkake, Sep 18, 2012.

  1. p1stov

    p1stov Member

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    i have tested on safemode with
    bcdedit /set useplatformclock true i get around 20-50 latency and hpet off on bios

    with bcdedit /set useplatformclock true and hpet on bios i get around 50-150 latency

    but im using amd processor, hpet is originaly created by intel... i think.


    picture with "bcdedit /set useplatformclock true" hpet off in bios
    [​IMG]
     
    Last edited: Oct 11, 2012
  2. p1stov

    p1stov Member

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    i have disabled all services except network.

    my best latency with all services disabled was 19-20
    i think there is no chance to go lower latency.

    mobo used GA-990FXA-UD7
    cpu amd FX-8150
    video nvidia palit 560 2GB
    ssd corsair force 3 90GB
    ram corsair 2x4gb 1600mhz c9

    i used this setings
    "bcdedit /set useplatformclock true" hpet off in bios

    [​IMG]
    [​IMG]
     
  3. IcE

    IcE Don Snow Staff Member

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    This doesn't make sense, the default option and option 1 are the exact same thing. Also, the default setting is no value at all, so /deletevalue returns you to default.
     
  4. hnizdo

    hnizdo Member

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    Latest nv drivers 306.97 made games smoother, namely Batman AC, but with HPET on I feel more stable and smooth fps in Arma2OA and Sleeping Dogs. I think fps are the same, but it feels like much more. I will keep monitoring this tweak and report.
     

  5. Phroster

    Phroster Master Guru

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    Option 1 is the default setting for windows (no setting) and HPET enabled in the bios.

    You can then use the bcdedit /set useplatformclock true command + HPET on/off.

    Or you can use bcdedit /deletevalue useplatformclock (no setting) + HPET on/off.

    This gives 4 different results when looking at the WinTimerTester.exe.
     
  6. HonoredShadow

    HonoredShadow Ancient Guru

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    No it does not. He is right. Their are only TWO.

    If you have HPET on or off in BIOS and not enabled in Windows. ITS OFF.

    If you have HPET on in BIOS and enabled in Windows. ITS ON.

    Thats it.

    If you have HPET on in BIOS but not on in Windows then its still off as you have not enabled it lol.
     
  7. tweakpower

    tweakpower Banned

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    On some PC's will work better with HPET on, on some with off, and on some, it would be the same.

    Currently, i can't care less about HPET since it works the same, but on some boards i had to disable it (in most cases it is ON by default).
     
  8. Mineria

    Mineria Ancient Guru

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    Sorry, your plain misunderstanding it.

    There are 4 combinations for Windows 7, 2008R, 8 and 2012:


    1. TSC and LAPICs:
      HPET disabled in BIOS, Windows (bcdedit /deletevalue useplatformclock "Windows default")
    2. LAPICs only:
      HPET disabled in BIOS, Windows (bcdedit /set useplatformclock true)
    3. TSC and HPET:
      HPET enabled in BIOS, Windows (bcdedit /deletevalue useplatformclock "Windows default")
    4. HPET only:
      HPET enabled in BIOS, Windows (bcdedit /set useplatformclock true)


    If HPET is enabled in BIOS makes Windows use it when ever code requests for it, besides using TSC for all other requests that need a hardware timer, that is option #3.

    If HPET is enabled in BIOS and if you run "bcdedit /set useplatformclock true", Windows will use HPET only and not TSC, which means your forcing a HPET single clock domain upon the OS. (option #4)

    http://www.acpi.info/
    http://www.acpi.info/DOWNLOADS/ACPIspec50pdf.zip
     
    Last edited: Oct 17, 2012
  9. snorge

    snorge Member Guru

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    nice explanation thanks.
     
  10. HonoredShadow

    HonoredShadow Ancient Guru

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    Well I have never read that their are 4 states. I bow to you knowing more then! No worries. I tried the 4 and their was only 2 differences. With it off my PC had lower latency but had bigger spikes. With it on it had higher overall latency but it did not spike as much.

    So in order which is meant to be the better option? HPET on in bios was default and obviously Windows off (default).

    Is their a supposed best to worst in the 4?
     

  11. Raiga

    Raiga Maha Guru

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    Some random spikes in DPC Latency doesn't affect FPS value at all.

    The only observable difference when you the spikes happen are, audio disturbance at those points (Mainly onboard audio).
     
  12. Mineria

    Mineria Ancient Guru

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    Depends on the BIOS implementation of these timers, some do it better than others, which is why you see different results from different boards.
    I would prefer a stable latency over a lower latency with high spikes, since those higher spikes can have negative effect on how fluid code is executed (how you might experience a game).
    Although, with HPET enabled in BIOS, useplatformclockset to true and EIST/C-States disabled, your overall DPC latency should be lower than with any of the other 3 options, since HPET by nature has much lower DPC latency by design.
    On the other hand, your going to use more power like that, since your going to override APIC's power saving features.
    It's kinda like removing the rpm limiter in a car, it can run faster but uses more gasoline. :D
    Although, on boards with proper APIC implementation you would hardly notice the difference.
     
  13. HonoredShadow

    HonoredShadow Ancient Guru

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    I have Intel Speedstep disabled but nothing else. How do you have your HPET?

    Do you have some power saving features turned off?
     
  14. Mineria

    Mineria Ancient Guru

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    I have HPET enabled in BIOS, all C states including speedstep disabled and useplatformclock set to Yes in Windows.
     
  15. HonoredShadow

    HonoredShadow Ancient Guru

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    Does that mean that your processor is going full blast 24/7?!

    Which ones could I disable apart from having mine for full blast? What would I be disabling?

    Like i said I disabled Speedstep but did not understand which was which of the states.

    Surely when your PC runs a game and the CPU goes to full then the latecy goes down just like disabling the states any way?


    EDIT: I just disabled all C-States just to see what would happen and put HPET enabled in BIOS and Windows. My current latency is between 15-30.

    Anyway I would still love to know if running a game does exactly what I have just now. In other words the game makes everything goto max and the latency then drops anyway. Therefore you don't need to turn off the states.
     
    Last edited: Oct 18, 2012

  16. snorge

    snorge Member Guru

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    I am pretty sure that is what would happen unless for some reason your cpu is downclocking randomly while playing.
     
  17. Mufflore

    Mufflore Ancient Guru

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    No.
    How can it unless you deliberately make your PC run at 100% continuously.
    You can check this yourself with task manager.
     
  18. HonoredShadow

    HonoredShadow Ancient Guru

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    I don't think you understood me properly and I think I am to tired to explain.

    He was on about C-States. One of them you turn off and your CPU goes at full speed constantly.
     
  19. Mufflore

    Mufflore Ancient Guru

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    I'm not understanding what problem you feel this causes apart from a 'small' amount of extra power use at idle.
    At idle, changing the voltage and response time of the CPU adds very little to power use.
    At full load, the voltage and clock speeds are at its *max anyway, so it makes no difference to power use because power saving measures are no longer applied.
    (*max being the max setting for load as it is configured to use)

    Changing C states doesnt make the CPU run at full speed constantly, it makes the clock speed stay at max.
    The CPU is still running at the same load, in fact the % load will be lower since it has more headroom at max clockspeed.
     
  20. tweakpower

    tweakpower Banned

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    Major problem here is that you guys mix up speed with frequency (alright, Mufflore maybe not). As he said, running CPU at max freq. have nothing with speed or usage. CPU runs at "full speed" (and usage) only with perfectly optimised application such as Prime 95. Speed of CPU is measured in OPS, freq. in Hz, and usage in percents (%), all of them, different things.
     

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