FSX hyper threading or not?

[Zap 2]

Thanks pH, I have yet to try setting affinity using anything external to FSX but seeing your positive results I certainly will give it a try.

 

PieEater, my system was very much like yours concerning max stable overclock and temps being about the same with or without HT.

 

If and when you try AM=244(00101111) I hope you will also try AM=252(00111111).  It will be interesting to see if you get the same flaky fps/stuttering I mentioned.

[Illegitimi non carborundum 4]

PieEater<br />I use Process Lasso instead of setting the AM in FSX and to me it runs smoother. There may be a demo version. http://bitsum.com/prolasso.php<br />There's another app out there (PRIO http://prio.en.softonic.com/) that does a similar thing, but I prefer PL. What I liked was that it sets the Affinity at the command level and its not a fixed value, so that may be optimal in core usage and I opined that might be more efficient than setting it within FSX. It certainly helps with core allocation - but I could just be deluding myself.<br /><br />I ran some tests on HT on my SB rig and saw a max rise of 2 deg C even at 4.6GHz so maybe Intel fixed the heat issue. I''ll try it on my i7 860 when I fit a liquid cooler I have on order.<br />Some excellent discussion here.<br />pH

[jjjallen 37]

I've been doing a bit of experimenting with my FSXAssist tool and found that HT does indeed yield better scenery and allows for a higher LOD.  Here are the best settings on my current build:

 

Cheers

Jim Allen

SkyPilot Software

[Zap 2]

Jim since it looks likely you're doing some methodical testing during the development of FSXAssist, if you haven't already, would you mind giving AM=244 a try?

[TheFamilyMan 279]

When I first got my i7 860, I wasted far too much time beating Hyper-Threading and the FSX Affinity Mask setting to death.  In the end I found that whether using HT or not, the default, i.e. no specified AM, was as good as, or better than, anything else.  The only reason I am currently not using HT with FSX is that I can reach a higher CPU OC without HT enabled.

[SAAB340 28]

 

1) Thread collisions manifest themselves as stutters within FSX.
2) FSX obviously doesn't need HT disabled in BIOS on single or dual core HT enabled CPUs, I guess because it automatically sets the relevent AM. In which case I guess it's safe to assume that you don't have to disable HT in BIOS on a quad (or greater) core CPU as long as you manually set the relevent AM.

 

1. Correct. you always get more stutters and most of the time lower FPS.

 

2. Well, I guess the answer is actually no. You can lower the risk a lot by manually tweaking the affinity mask when you have HT on. But as soon as HT is activated in BIOS there's a 2nd virtual core exposed that will share the same physical CPU core as FSXs Main-Thread. The risk here is that Windows shedules something to run on that core, because if it does, it will steal CPU time from FSXs main-thread - 'colliding' with it.

 

Yes, Windows could always shedule other threads (from both FSX and other applications) to run on the same physical core as FSXs main-thread even when HT is selected off in BIOS. But it's very very unlikely. Because FSXs main-thread will run at full core load all the time. As long as Windows has a core with lower load availible it will most likely shedule any other threads there. Why put more work to a core thats already occupied when there's other cores that have spare cycles? (Thats why we de-select a core in the Affinitymask even on a quad-core without HT to make sure Windows always has a core with low load on it to shedule other-threads on.) 

Having HT on in BIOS always exposes a Core, that shares physical core with FSXs main-thread, with no load on it that Windows might see as a god place to schedule other threads on. You can always reduce that risk by tweaking the affinitymask but the risk will always be there as long as HT is on in the BIOS.

[SAAB340 28]

To answer the OPs question. It depends what you are after when it comes to performance. My reccomendations are:

 

If you value groundtexture loading and loadtimes more than FPS, leave HT on and use an apropriate affinity mask. 249, 241 and 244 are 3 good ones to try with.

 

If you use your computer to other things that make good use of HT but wan't the best FPS and can live with a increased risk of stutters and lowerd FPS every now and again leave HT on and set affinitymask 84. 

 

If you want the highest FPS and least risk of stutters in FSX all the time turn HT off and use affinitymask 14, 13, 11 or 7.

 

If you can't be bothered and just want to fly, leave HT on and let FSX use it's default affinitymask (85). It still does a good job in a lot of scenarios and in general does a slightly better job than HToff with default affinitymask (15).

 

I personally use my computer set at stock speeds normally with HT on and have affinitymask 249 set in the .cfg. I don't have a rig exclusivly for FSX.

If I know I'm gonna sim with a lot of photoscenery i overclock my CPU with HT on and leave my cfg untouched.

If i know I'm gonna sim with complex aircraft and big airports I overclock my CPU with HT off and change the affinitymask to 13.

[Emile 28]

Hello,

"If you value groundtexture loading and loadtimes more than FPS, leave HT on and use an apropriate affinity mask. 249, 241 and 244 are 3 good ones to try with"

 

I am testing the "249" and it works very well.

I was using the "255".

[SAAB340 28]

255 is a no-no affinity mask. Anything putting a t&t loader on the same physical core as the Main-thread is. Just because it shows activity in the task manager doesn't mean that it's good activity...

[Guest]

If you have a more modern CPU and run Windows 7, I'd leave Hyper-threading enabled.  Intel have done a lot of work to ensure hyper-threading is more efficient.  Microsoft have also improved threading support in Windows 7 (and Windows 8).

 

But as has been suggested, try it and see -- really is the best approach.

[jjjallen 37]

I tend to agree that HT is the way to go with a modern OS like Windows 8.  Just realize that your core temps will be much higher so reduce your overall OC and core temps accordingly.

 

Cheers

jja

[PieEater 10]

Just realize that your core temps will be much higher so reduce your overall OC and core temps accordingly.

If you refer back to posts #14, #16 & #17 you will see that this is not neccesarily true. I notice you have an Ivy Bridge CPU is it perhaps something that affects these rather than Sandy Bridge (which the OP has)? How much do your temps rise with HT enabled?

[jjjallen 37]

Hi all - FSXAssist has been in continual improvement since its original release with many improvements implemented.  At any rate PLEASE do not use the original AVSIM library beta release as it has some significant defects that have since been resolved.

 

The current payware ($12.95US) version of FSXAssist is 1.04 and can be downloaded here.

 

A new build 1.05 is pending release in the next few days and fixes an issue with loading FSX modules that one user has reported and also changes the reload timings for FSX crash detection.

 

Regards

Jim Allen

SkyPilot Software

[ozflyer 2]

Sorry to bump an old thread.

 

What is the recommendation for a dedicated FSX machine, keep HT on or off ?.