I have been working on setting up FSX on my computer for a couple of months now. I have added REX2, GEX and UTX and am using ASE as my weather engine. I am now tweaking FSX to make it look and perform as good as possible. At the moment I have HT turned off on my I7 2600K CPU. Is this the best configuration for FSX or does it run better with HT turned on?

Popular opinion says, turn HT off, especially if you are OC.

You will get conflicting information on that discussion. I've used FSX (w/ASE) both with and without hyperthreading turned on, and I can see absolutely no difference in the performance of the game. Frames, smoothness, stutters... all perceptively unchanged from one setting to another. HT does have some semblance of benefit to other, non-MSFS applications, so I would recommend turning it on and seeing if you notice a difference. You likely will not, and the benefits will help you outside of the game. My vote is keep it on, as the processor is intended to operate. -Greg

It may and probably will on some system produce more stutterings, for sure will produce more heat as you will also need more core voltage to keep your CPU at the same GHz stable with Hyperthreading on. I tried it on my system and I had to raised the core voltage to stay at 4.677GHz stable with HT on, I also had more stutterings in FSX. Try it and see how FSX will run with and without.

Thanks for the input everyone. I guess I will try it both ways since there seems to be multiple opinions on this issue.

FSX needs a fast overclock, so the important opinion is how fast can I overclock, and can I keep the temperature below XX degrees. That means HT off.

FSX needs a fast overclock, so the important opinion is how fast can I overclock, and can I keep the temperature below XX degrees. That means HT off.

Hmm... guess my i7 990 Extreme (6 cores+HT) at 3.47ghz (not overclocked) running over 50fps with all scenery sliders to the right is a complete and absolute fluke??

Hmm... guess my i7 990 Extreme (6 cores+HT) at 3.47ghz (not overclocked) running over 50fps with all scenery sliders to the right is a complete and absolute fluke??

Your chip is not a fluke, you're just the first one to make such a statement. Most systems, if not all, require fast CPU clock speed, over 4ghz, to run FSX acceptably. That's above 20 fps and smooth. If yours can run smooth at 50 in NYC with SC & AG , water to the right, using a PMDG jet or flying the Mustang, with poor weather, and 50% AI, then...... Maybe you have a super chip at 3.47? No need to OC yours.

Presumably, you have a system with 4 cores and 8 threads. Turn off hyperthreading and ensure you use the affinitymask tweak in your FSX.cfg and set it to 14. Affinity mask 14 should use cores 1, 2 & 3 for FSX leaving core 0 to run the operating system, background processes, etc. This generally results in a much smoother FSX. IAN

Hmmm, I run a i7 2600K at 4.8ghz with HT on, and I set the affinity of FSX to all cores which is 255, I shut of various services etc and have FSX on realtime, I have all sliders at max and get around 20 fps at heavy airports, in saying this if I have HT off I get 20 fps at heavy airports......no diff to me, remember you only need to be flying at a dif angle or position and that will determine what the processes are based on autogen etc to change your fps unless you fly exactly in the same position to try and determine you true fps.

I run with hyperthreading ON. I see no difference between on vs off. I have tried all the affinity mask settings to take advantage of both situations and I have see 0 difference. I like the OS having more logical processors to play around with.

Hmm... guess my i7 990 Extreme (6 cores+HT) at 3.47ghz (not overclocked) running over 50fps with all scenery sliders to the right is a complete and absolute fluke??

Wow... @3.47 running over 50fps? I suspect no addons, all default?

Temperature is the reason for HT off, as it creates a hotter environment if it's left on.It's really a hold-over from the i7-9xx series, but still somewhat relevant as we get up into the 5.0-gig territory. An i7-950 (my old bee-yotch) runs at 71 degrees, 4.48 gig, and is/needed water cooled. Turning HT on will add another 5 - 10 degrees of heat to it, and it would not come close to 4.48 on air, whereas my newer i7-2600K just bee-bops along at around 45 - 50 at 4.8-gig. It just happens to be water-cooled, but doesn't need it. NB: At 3.47 gig, Ed you're not seeing half of what this sim can do, and saying "over 50fps with all scenery sliders to the right" is a pretty ambiguous statement, and can mean absolutely everything - or absolutely nothing.Show me a continuous, solid 30fps, in the Maddog, OrbX PNW at KSEA, with (MTX) 30%AI, 20%GA, 15%road, 25%airport traffic; REX 1024 x 1024 clouds, using the Aussie Weather - 1000', base, 9500' tops; water at High 2.x; AG and SC at Very Dense; LOD 5.5; Mesh Comp 75; M. Res 10m; Text. Res 3-cm; at 3840 x 1024 x 32bit, Aniso and AA, plus the Inspector setting settings per Nick Needham... Right - it won't do it; not at 3.47 GHz. But the 2600k sure as heck will at 4.8 and above, and a lot cooler than the 990. Statements like yours do a strong disservice to the guys like ******* Altuve and Nick Needham - plus all of the other outstanding developers and forum members that have contributed their thoughts and ideas to help us get the very best experience we can from this great sim - and I'm sure you take the benefit of their efforts, too, right?

FSX totally ignores SMT. If you have four physical cores and four virtual ones, FSX will only use the four physical ones. Turn off HT when using FSX.