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Old 12-12-2012, 12:01 PM   #1
Anarchist420
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Default What if I disable High Precision Event Timer?

What would happen if I disabled HPET?
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Old 12-12-2012, 01:06 PM   #2
Anarchist420
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Quote:
Originally Posted by tweakboy View Post
What motherboard do you have Anarchist420 ? I would disable crappy things like that in the BIOS. gl
Sabertooth P67 B3 by Asus.
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Old 12-12-2012, 02:22 PM   #3
Anarchist420
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2500k 8GB
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Old 12-13-2012, 09:29 AM   #4
ShadowVVL
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Quote:
Originally Posted by Anarchist420 View Post
What would happen if I disabled HPET?
I was wondering the same thing about a year ago.never really understood what hpet did other then it was a cpu or I/O timer of some kind.

I just left it alone.
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Old 12-13-2012, 09:31 AM   #5
imagoon
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HPET is mostly used for multimedia / syncing media streams with audio. If you disable it, the OS / app if it uses falls back to RTC and may start desyncing video. I can't really think of a good reason to disable it unless your systemboards implementation is crap (it happens). You also may need to force Windows (no idea on Linux) to only use HPET so the CPU isn't wasting time syncing all the rest of the system timers.

bcdedit /set useplatformclock true (then reboot) enable HPET
bcdedit /deletevalue useplatformclock (then reboot) disable HPET

Mileage varies like all changes to computers.
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Old 12-13-2012, 09:38 AM   #6
ShadowVVL
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Thank you imagoon for the explanation.hpet is no longer a mystery to me
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Old 12-13-2012, 09:40 AM   #7
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Quote:
Originally Posted by ShadowVVL View Post
I was wondering the same thing about a year ago.never really understood what hpet did other then it was a cpu or I/O timer of some kind.

I just left it alone.
HPET is a high resolution timer. RTC is normally around 3.4mhz where HPET is around 14mhz. The idea is that at say a 3ghz cpu speed, a lot can happen between clock ticks and it can be enough to start desyncing video / scientific work. Example:

@3.0ghz -> about 882 cpu cycles occur between RTC ticks
@3.0ghz -> about 215 cpu cycles occur between HPET ticks (also is typically 64bit counters)

The main issue comes from how the timers are used. If they are sending interrupt based ticks, the CPU has to spend time handling those interrupts which happen more often in HPET so the balance is to increase timer resolution while not overloading the CPU with timer work.

Add in that Windows 7 / Linux by default tries to manage all of the system timers and keep them synced, this can cause some CPU loading issues. Using the platform clock tends to clean this part up though because, in Windows at least, it makes windows only use HPET which can improve the system performance.
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