Intel Hyper Threading - on or off?

[SteveW 1,792]

I just started using an affinity mask of 150401 in my I7-5960X (8 core/16 thread) I'm now getting 60 FPS locked with high settings, smooth as butter.

I'm not surprised that's the proper way of doing things. However, 150401=(10,01,00,10,11,10,00,00,01) accounts for 9 cores with 18LPs, we should use an 8 core 16LP AM for the 5960x, but it makes no real difference, although with your AM the leftmost "10," is ignored.

 

Instead you can rearrange your AM for 8 cores 16 LPs for clarity.

 

54272=(11,01,01,00,00,00,00,00) = 4LPs

62720=(11,11,01,01,00,00,00,00) = 6LPs

64832=(11,11,11,01,01,00,00,00) = 8LPs

 

Each of these gives the first two main processes a core of their own with the others ganged on a core. You should get the same performance from these.

[SteveW 1,792]

This discussion was long since answered - to recap:

 

We should use HT enabled since it improves task switching. Some say unless we are pushing for a very high overclock and HT=Off reduces heat, but that's open to another debate, the trade off between a few more MHz or HT enabled.

 

With HT enabled we can help the OS to give the sim uninterrupted throughput by the use of an Affinity Mask. We can keep the main P3D process on a core of it's own, helps the OS to decide to place the next sim thread along to the next core, before the sim is fully started and maximising it's primary core. Once the sim is running the jobsheduler should keep new processes off that core since it will be maxed my then.

 

If we allow the sim to spread it's threads across many cores, we can have too many secondary threads stopping the main thread to communicate, and that starts to eat into the smoothness of the sim.

 

With HT=Off the AM becomes more important when we have many cores, we can partition the CPU and provide adequate cores for the sim, leaving the jobsheduler to find lesser used cores for new processes.

[Slayer 190]

I'm not surprised that's the proper way of doing things. However, 150401=(10,01,00,10,11,10,00,00,01) accounts for 9 cores with 18LPs, we should use an 8 core 16LP AM for the 5960x, but it makes no real difference, although with your AM the leftmost "10," is ignored.

 

Instead you can rearrange your AM for 8 cores 16 LPs for clarity.

 

54272=(11,01,01,00,00,00,00,00) = 4LPs

62720=(11,11,01,01,00,00,00,00) = 6LPs

64832=(11,11,11,01,01,00,00,00) = 8LPs

 

Each of these gives the first two main processes a core of their own with the others ganged on a core. You should get the same performance from these.

 

15 04 01 - was my somewhat poor attempt at an april fool but noone detected it

[SteveW 1,792]

haha, good one!

[toby23 136]

Steve, thanks so much for sharing your knowledge.

As always, it's a pleasure to hear you explain everything clearly and intelligently.

 

I wrote a ''how to'' post a while back for Prepar3d v2 and thought that it would become out of date based on how LM was planning to open all cores to P3D.

What I hadn't considered was the knock-on effect that opening all cores to P3D might have..

 

Thanks to your posts here, I have revised my thinking and am now using a mask in v2.5 as well, freeing up 4 threads for the system and other apps, while P3D is restricted to 4 of its own threads.

Thanks again for your time and help.

[SteveW 1,792]

You're welcome Toby! 

[dokelly07 0]

I have a 3770k overclocked to 4.2 with HT=on.  I was running it off but was interested in switching over.  With HT=on and an affinity mask of 244 I am seeing much better results.  Not a placebo for sure.  Tested over Orbx San Carlos facing San Francisco.  Never dipped below mid 30's while locked at 40.  I was always dipping into the mid-20's prior.  Also tested over other orbx areas an can confirm for my setup this is the way to go.  I am liquid cooled so not worried about any additional heat.

 

Is there another affinity mask setting I should be using?  I like what I have and might just stick with it, but wanted to make sure I had it set up right. 

 

HT=on in bios

cores unparked via registry, confirmed via unparking tool

 

in p3d config......

 

[JOBSCHEDULER]
AffinityMask=244

 

Thanks for this thread, it has made things much easier on the eyes.  Still waiting on true fullscreen mode though so I can run the 1/2 refresh rate vsync option like i did in FSX....that will be magical.

[Michael Moe 495]

I have a 3770k overclocked to 4.2 with HT=on.  I was running it off but was interested in switching over.  With HT=on and an affinity mask of 244 I am seeing much better results.  Not a placebo for sure.  Tested over Orbx San Carlos facing San Francisco.  Never dipped below mid 30's while locked at 40.  I was always dipping into the mid-20's prior.  Also tested over other orbx areas an can confirm for my setup this is the way to go.  I am liquid cooled so not worried about any additional heat.

 

Is there another affinity mask setting I should be using?  I like what I have and might just stick with it, but wanted to make sure I had it set up right. 

 

HT=on in bios

cores unparked via registry, confirmed via unparking tool

 

in p3d config......

 

[JOBSCHEDULER]

AffinityMask=244

 

Thanks for this thread, it has made things much easier on the eyes.  Still waiting on true fullscreen mode though so I can run the 1/2 refresh rate vsync option like i did in FSX....that will be magical.

 

 

Hmm i always have run FSX and P3D with HT=off. Guess its just an old/forgot thing with me.

 

What should i try with a 4770K ? (AM setting )

 

And what is unparking ? and how ? :-)

 

Is there a tool i should use when having HT=on ?

 

Thanks

Michael Moe 

[dokelly07 0]

I started out running P3d with no HT but converted as you read.  I feel that it is significantly smoother (for me).  Just google "unpark cores" and that should take you on your way.  You can use a tool that is free to download or you can do it yourself following directions and editing your registry (that's what I did).

 

Read through this thread and all questions you asked are answered including how to figure out the affinity mask for your setup.

[Noel 4,492]

This discussion was long since answered - to recap:

 

We should use HT enabled since it improves task switching. Some say unless we are pushing for a very high overclock and HT=Off reduces heat, but that's open to another debate, the trade off between a few more MHz or HT enabled.

 

With HT enabled we can help the OS to give the sim uninterrupted throughput by the use of an Affinity Mask. We can keep the main P3D process on a core of it's own, helps the OS to decide to place the next sim thread along to the next core, before the sim is fully started and maximising it's primary core. Once the sim is running the jobsheduler should keep new processes off that core since it will be maxed my then.

 

If we allow the sim to spread it's threads across many cores, we can have too many secondary threads stopping the main thread to communicate, and that starts to eat into the smoothness of the sim.

 

With HT=Off the AM becomes more important when we have many cores, we can partition the CPU and provide adequate cores for the sim, leaving the jobsheduler to find lesser used cores for new processes.

Hello,

For my SB-E chip w/ HT on I've always used AM 4094, or 111111111110.  Does this fit w/ what you are saying for optimal task switching on the main thread for P3DV2?  I seem to have always had excellent results in terms of texture update rate and frame rate is as good as it can be give my 4.4Ghz overclock.

 

Thanks!

[Michael Moe 495]

Hmm i always have run FSX and P3D with HT=off. Guess its just an old/forgot thing with me.

 

What should i try with a 4770K ? (AM setting )

 

And what is unparking ? and how ? :-)

 

Is there a tool i should use when having HT=on ?

 

Thanks

Michael Moe

 

 

Just an update.

 

I tried it out with AM=254 which seems to leave core0 not busy. Sometimes all other cores are doing something. No other addons in background.

Seems smooth and sharp. A little lower clockspeed but only 1-2 fps lost so far.

 

Any other recommendation apreciated all though i think this might stick

 

Michael Moe

[Bob Scott 7,718]

Bringing this discussion to bear on P3D V3 now. I just did a little experimenting (i7-4790K, HT ON).

With no affinitymask, there was some (slight) choppiness at times, where AM=244 (11110100) put the P3D core on LP 3 (and physical core 1) by itself, with other processes free to use core 0. Noticeably smoother in the spots where I saw some minor microstutters before, though not dramatically so. Still, I think the out-of-the-box P3Dv3 might still be able to use some help with an appropriate AM setting.

Regards

[Manny 1,293]

P3D auto settings is equivalent to setting AM=0, or 255=(11,11,11,11) on your HT enabled 4 core

 

Can also try: 212=(11,01,01,00) or 245=(11,11,01,01), or 253=(11,11,11,01).

 

...things pan out differently depending on monitor number and size, autogen, photo-real, weather intensity, etc. That's why a range of setups should be tried.

 

Is that for 4 cores with HT on?

 

my 4 core (3770K OC to 4,5Ghz) without HT I prefered 15 over 14. This way all the cores were used by P3D and the blurries were considerably improved.

 

I just turned back on the HT.

 

So now  I have 4 cores with HT and I just did my AM to 168.. and trying it out.

 

Would like more options... 

 

OK.. 245 is better than 168 and HT is so much better...  Need to try  253 after this. I feel like I just upgraded my CPU

[Jazzfan 57]

   Manny, 254 may be a better choice for your AM. The best advice I found for my setup came from this thread;( referenced by Toby23 above) http://www.avsim.com/topic/444793-one-tweak-to-rule-them-all-how-to-set-affinity-mask-correctly/

   It's very informative, and explains very well (using the built in Windows calculator) how to determine the correct AM value for whichever cores you choose to use.

 

  Regards, Craig.

Edited October 9, 2015 by Jazzfan

[Cargostorm 151]

Tried HT ON/OFF with and without AM (254) in P3D V3.

 

With HT ON less FPS and much higher temperatures (84 deg C.) with 4790K @ 4.5 GHz.

I leave HT OFF.