I have been fighting sudden appearance of stutters and lower FPS for a couple of months now and it was driving me nuts. Then I read this article on ASUS MB having HPET (High Precision Event Timer) enabled in the BIOS. The article (which I can't find now) claims that  it is a source of stuttering/pausing in games (Skyrim) that are CPU dependent.  Reading further there is some controversy over whether it should be on or off, the author claims off is better. So I followed some simple instructions to determine if mine was on and if Windows 7 had it enabled. It was on and enabled. So I disabled HPET in windows and turned it off in my BIOS...I was astounded at the immediate and quite noticeable difference. FSX got 20% FPS increase in my system and now it is virtually stutter free. Mind you, this worked in my system, your mileage may vary. Oh yeah, it also fixed my very annoying "G" key lag on my keyboard.

 

If you are interested in turning it off, this is how I did it. Do this at your own risk, if you don't know what you are doing learn about it first, I am not liable.

 

Bring up your CMD window under Admin and type in this command bcdedit /deletevalue useplatformclock

If you get an error about element not being found, then HPET is disabled in Windows and isn't being used. If you don't get an error message, and you get a confirmation, then it is most likely enabled and now it is not, due to that command you gave. If it is not enabled in windows, make sure it is off in your BIOS if you have it, this could cause problems of its own, according to the article AFAIK.

 

To enable HPET Bring up your CMD window under Admin and type in this command bcdedit /set useplatformclock true

 

To turn HPET off/on in your BIOS, if you have it, refer to your motherboard's manual.

 

Hope some of you have success with this as I did. This changed FSX for me. Hopefully there isn't some program that relies on HPET, I doubt it, but who knows?

If you have a fairly new system, then yes, this should be off. It was posted by a Avsim user on another thread that HPET is old tech, and should be off on the latest and greatest.

I have an aging system, 2600K and GTX580, and HPET works great for me and stops stutters and increases FPS.

Any system newer than a 2600K should have it off.

The funny thing is, I don't need to upgrade my CPU with HPET on, as I now gain the performance I want.

I turned it off and was like holy ****. The difference was amazing. Running serious hardware I did think it was underperforming a bit. This made a world of a differnce.

Just my luck, I start a 5 hour flight from iad-san in the PMDG NGX... After landing I am going to check this, thank you

Sounds interesting, I'm going to have a look...

I had just wiped and rest my BIOS last month and this was enabled. Now off to see if it makes any difference in fsx after disabling it... WOW you weren't kidding, this gave me at least 5 more fps

Stutter city for me - thanks anyway Ric

Couldnt find it in my gigabyte b85m-d3h bios and it was off in win8.1. Oh well...

arnava, it is probably under Power Options. From what I understand, it can be Off in Windows, but if it is On in your BIOS, you will get the HPET timer + some other kinds of timers, and that isn't optimal. So I think the key is to either turn it Off in both places, or On in both places. Even though it is Off in Windows, it might be Enabled in BIOS by default, so you still have to check. I wanted mine On. It was Enabled in Bios, but set to 32, so I changed it to 64. Then I went into Windows and did the bcdedit /set useplatformclock true. Hard to tell yet, if there is any performance affect, but I don't think it made anything worse.

In my case it was on in bios and off in W7 , running some tests now.

Mine was enabled in bios but not win8.1, so I enabled it and p3d stuttered. I disabled in bios and win8.1, will report findings.

After a bunch of research:

 

HPET is a multimedia timer built into your southbridge chip Intel started using them circa 2005

 

There is a newer timer called TSC  

 

Windows 7 it could be on or off depending on your hardware but for most Windows will use TSC, Windows 8 uses TSC by default.

 

TSC uses much less overhead than HPET but TSC isn't ideal in all situations so the HPET timer is used as a fallback. Should HPET be disabled it will fall back even farther to yet an older standard( can't recall what it is)

 

Intel chips of Nelahem or newer support the newer invariant Time Stamp Counter(TSC for short)

 

Bottom line for most of us is to leave the HPET enabled in BIOS and have it off in Windows. Windows will use the TSC counter but still have the fallback capability of HPET as need arises.

 

I did a bunch of FPS tests and checked for stutters with a DPC latency monitor running. There was hardly any difference.

If you run SLI it helps a lot. Having it disabled. 

HPET was "off" in Windows 7 by default, but enabled in BIOS for me. So, I I made the attempt and turned it off , but saw no appreciable performance change to my eyes. More importantly, I had my first full-on "blue screen of death" in years with the precision timer set to disabled in BIOS.... It was under heavy processor load and the BSOD warning noted specifically a problem with the interrupt clock.  Coincidence? Probably not.

 

So, based on no noticeable performance difference for me AND some newly introduced instability (referencing the interrupt clock) make this one a no-go for me.

 

(i7 processor on an Asus P9X79 Pro mobo, for what that's worth)

 

-Greg

What happens if you disable the HPET when some application needs it?