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dburne

Hyperthreading - and Stuttering

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Hey gang,

 

Ok so I know this has been discussed in the FSX forums in the past, this afternoon I was reading up on another flight sim forum I subscribe to - a combat flight sim - and this topic was being discussed there,

The Intel I7 core processors utitlize a feature called hyper threading, which is typically enabled by default , in the motherboard's bios. I have always left mine enabled. It basically gives you virtual cores, so with a quad core processor it also gives 4 virtual cores, or 8 threads of processing overall. Pretty simplistic explanation but that is how I look at it.

 

As I understand, not many games - if any, are coded to take advantage of these virtual cores. Heck most are not coded properly to take full advantage of the 4 cores of the processor.

So anyway the topic of stuttering was being discussed on that other forum , and many were reporting disabling hyper threading reduced, or often eliminated, the stuttering. Again I know this has been discussed in the FSX forum as well and many of you are already aware of this.

 

So this afternoon I decided to give it a try myself. Now on my system, really the only time I saw stuttering - and it was fairly minor, was when in the exterior fly by view over dense terrain. Then I would get minor stuttering.

I went into my bios, and disabled hyperthreading. I then ran a job as a test. Turns out, this seems to have elimated that minor stuttering I was getting in that exterior fly by view over dense/populated terrain. I saw no stuttering at all in that view - for the first time.

And, an added benefit - my cpu cores ran from about 8-10C cooler during the flight, with hyperthreading disabled.

 

I think I will just leave it disabled for a while. Windows may take some advantage of hyper threading, and some windows programs, but if they do I am not sure I would really notice any difference.

 

So if any of you are experiencing stuttering, and you are running a system with hyper threading, consider disabling it. In my motherboard's bios, it was referred to as " Intel HT Technology".

Of course, I may be the only one here left that was running with it enabled... :smile:

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If disabling HT makes your system run better... it's not the game that's the problem. Honest.

 

I have never, ever found a valid reason to disable HT (but I don't overclock either). Disabling HT in the newer CPU's is done more for heat reduction than anything else.

 

Just because a game can't take advantage of HT doesn't mean your OS can't. In fact, your OS will perform far better with HT than without.

 

Also, just an FYI: The Eaglesoft Citation X v2.0 for FSX takes advantage of multi-core/HT to give greater visual performance... thus disabling it in that regard would really mess things up.

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If disabling HT makes your system run better... it's not the game that's the problem. Honest.

 

I actually did not say it made my system run better, but it did apparently elimate the minor stuttering I was getting in Flight. I have not run the system long enough yet to see if I notice any difference overall.

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Flight running smoother and the computer running cooler seem to be two valid reasons for disabling hyperthreading. If the performance of a particular FSX aircraft and perhaps Solitaire or some other Windows program suffers that's certainly a consideration. I, personally, would see how Flight performs on my system with hyperthreading on or off but as I have an AMD processor I can't.

I'd especially like to compliment Don B on the thoroughness of his post. The acknowledgement of the source of the information provided and the outline of the procedure to evaluate the effects serves as an example of the right way to share information. Simply making a blanket statement without providing any means of validation can often be worse than useless.

 

Jim F.

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I can't say I've done performance testing with Flight although I did extensively with FSX. In any case, it is much more complicated to use hyperthreading with graphics to keep them "in time".

 

Let's say the HT i7 has 0,1,2,3,4,5,6,7 with 0,1 on one physical core, 2,3 on the second physical core, etc. With non-HT, it's 0,1,2,3. Now, let's say you have 4 processes. On 4 physical cores, the work would be done at approximately the same rate because they are distributed to on 0,1,2,3, all physical cores. However, if you have HT enabled, the game has to be smart enough to distribute this work on only the "even" cores or "odd" but not both. 0,2,4,6 would be fine so would 1,3,5,7. Otherwise, if it distributed to even and odd, the you could be only using 2 physical cores, 3 physical cores, or 7 physical cores.

 

To complicate matters, the video driver has to understand this as well, and the thread that is loading graphic tiles also has to.

 

There is almost no advantage with a game to have HT enabled. I'd turn it off unless you are folding or doing some other work that can deal with work that is not dependent on order.

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I'd especially like to compliment Don B on the thoroughness of his post. The acknowledgement of the source of the information provided and the outline of the procedure to evaluate the effects serves as an example of the right way to share information. Simply making a blanket statement without providing any means of validation can often be worse than useless.

 

+1

 

I had HT disabled on my previous CPU and this is why I went for the i5 2500K during my last hardware upgrade: it's about the same as the i7 but has no HT. I am sure HT has its advantages but while having the OS (or a specific program) running faster is fine and all, running a flightsim with (even slight) stutters is very annoying so to me the choice was easy. I doubt if I will actually notice the difference in speed in the OS itself (which to me is freakin' fast already, specially since I have SSD's), while I do notice stuttering in a game (if there is any).

 

Apart from that, I do OC my CPU's which was another reason not to bother with HT.

 

P.S. Welcome to the forum jimh425!

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I had HT disabled on my previous CPU and this is why I went for the i5 2500K during my last hardware upgrade

 

Oops! I just purchased that same CPU i5 2500 @3.3GHz, but I thought it was HT ????

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Oops! I just purchased that same CPU i5 2500 @3.3GHz, but I thought it was HT ????

 

No, the i5 2500 has no HT... Did you get the 2500 or the 2500K...? If you don't have the K-version you can forget about overclocking too...

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Mine's the 2500 (no K). Whow... the things FLIGHT makes me aware of.... :-)

 

Anyway, FLIGHT has very well settled now as THE FLIGHT SIMULATOR of choice for me, so, I don't really mind having bought the i5 (even if now I feel mad at me for not having studdied the lesson well before buying :-( ). If FLIGHT runs with less stutters in this system them I am fine with that :-)

 

I seldom use even ELITE now...

 

This weekend I took all of my available PC leisure time to "fly" FLIGHT, and it was REALLY GOOD!!!! :-)

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Thanks guys,

 

I guess the verdict is still out, I still need to do some testing in my other flight sims as well as seeing if any noticeable difference in running regular windows programs - I expect I probably will not see any.

If there were, it is easy enough to enable and disable HT during a restart or upon booting up, but may in fact end up just leaving it off as I have it now.

 

Thanks for the compliment jandjfrench, and also welcome to the forums jimh425 and thanks for the info!

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You are welcome. Thanks for the welcome, but it's a welcome back. I was here a few years ago before the site was hacked. At that time, I was in the ESP/FS studio before execs at msft lost their mind and shut us down. ;)

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Xiiiii that's when I lost my account too!!!!

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No, the i5 2500 has no HT... Did you get the 2500 or the 2500K...? If you don't have the K-version you can forget about overclocking too...

 

This is something that has me scratching my head in puzzlement. I have a 2600 (non-K), which "everyone" assures me cannot be overclocked...

 

...yet, using the options in the Advanced BIOS menus, I've been easily able to overclock this processor from the stock 3.2 GHz to 4.2 GHz...

 

...I also have a 2600K for my primary flightsim rig, and have used the same Advanced BIOS settings as I did with the 2600 (non-K) machine :unknw:

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Hello Bill

What you are seeing is the limit of intel turbo boost which all Sandy bridge can do automatically, no need to force anything in the bios.

What folk mean by the non K series not being over clockable is not being able to go beyond this.

Try taking your non K series up to 4.8 then do the same to your K series chip, one will do it, the other will top out at 4.3 ish

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Here is a nice graphic displaying the difference of the 'K' SKU:

 

19b35b81_vbattach189639.jpeg

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After some more testing, it is obvious that for whatever reason, disabling hyperthreading has made Flight smoother for me - got rid of the minor stutters I was seeing when in fly by external view. That was the only time I saw this minor stuttering, glad that is gone. I have checked and rechecked it flying over some very populated areas, and very dense terrain - smooth as silk.

 

I have only briefly tested it with a couple of other flight sims I have, combat sims, and so far looking pretty good there as well. One of them is notorious for having some stuttering while engaged in a battle with explosions, etc - I need to do some more thorough testing with it and see if it has improved.

 

I also need to go into FSX and test it there as well to see if it helps with it's stutters, I know that is one of the things many recommend doing to help it, disabling hyperthreading , and even setting processor affinity.

 

Still probably to soon to tell if I will notice any difference in day to day usage of my computer, so far I certainly have not seen any difference.

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Hi

 

And don't forget that if your system's running cooler that's an indication that less power is being consumed. It's saving you money continuously and making for a greener environment.

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Good point, thanks.

Yes it is definitely running cooler, a nice side benefit.

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I bought mine not even guessing it had no HT, but I am now glad I did... Yesterday a friend of mine who is in charge of the PC maintnance at the office commented when I mentioned my i5 had no HT: HT sucks.... You're fine with that :-)

 

I am !!!! FLIGHT indeed runs smooth as silk...

 

I was considering an incursion into the military side of simulation, just for the sake of the great detail the DCS p-51 brings, but I have decided I will stick with FLIGHT *** ONLY ***, no more diversions with XPlane, FlightGear, and even ELITE and Condor are almost abandoned on the Programs(x86) of my Windows 7 :-)

 

This weekend I did lower the scenery density but it was just for making it easier to complete some of the gold coin challenges :-)

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I will always get a processor with HT available, rather than one without. The reasoning is the same as some have used regarding cockpit-less planes. I would rather have the option to use or not use a given feature be available to me at my own discretion rather than have the option be removed from me completely.

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What Ed and JimH said above ^^^ - just adding my two-ha'penworth as I have been looking into this quite a bit lately (and I like the sound of my own voice :wink: )

 

I'm in no way an expert on CPU architecture, but I can read, and have read the Intel docs on their site http://www.intel.com...ion-manual.html <--Brain-pain inducing stuff that...

 

Also see See: http://en.wikipedia..../Hyperthreading

 

HT is app-specific i.e the app (through Windows threading scheduler) needs to be able to use it properly, or, as JimH says above, most "older" games will not use it.

 

The rule is usually: if you have more intensive threads than you have physical cores, then you will see a benefit from enabling hyper-threading..

 

An HT CPU is able to run virtual multi-threading (hence the name) They are not virtual "cores" as such, just the ability of a real core to run a virtual "twin" pipe of data. (crucially, it's not always a 50-50 split)

However, as far as any multi-threaded apps are concerned, the "virtual" core and the real core are essentially identical. Any process running on either the real or virtual core will run at exactly the same speed. (or so the theory states)

 

The only time this will impact anything is when you have two processes running on the same core at the same time, hence the AffinityMask setting some ppl use with FSX - I took mine out at the suggestion of a much more experienced FSX tweaker than me, and it had no discernible negative impact (but now I've disabled HT altogether to see if I can cure my P3d stutters - and yes it can!)

 

The actual mission statement for HT from Intel goes thus: improved support for multi-threaded code, allowing multiple threads to run simultaneously, improved reaction and response time. (among others)

 

And, as Ed also says above, Windows (and most modern productivity apps) WILL use it, to the max, (esp stuff like 3DS, Maya, Photoshop and good video editing apps) so, following that logic, and as Ed says above also, leave it enabled for anything other than games...This is problematic, however, as you have to enter BIOS to turn it off and on..

 

HT is not your enemy, but it can (very rarely) cause issues..FSX being (for some ppl) one of them (and FLIGHT it seems)

 

With a super-bad CPU and mobo pair, utilising a modern, super-bad memory controller, (and according to the real experts on these forums) you don't really need HT unless you are running a render-farm or doing on-line video editing (for which you'll also need a super-bad video controller) or super number-crunching for scientific purposes..

 

Despite it's obvious benefits, most modern hard-&amp;@(&#036;* CPU's don't really need to use it (or their soft, fleshy operators won't notice it much, if at all in their day-to-day lives)

 

But Don, you have hit upon a great reason for turning it off: Heat. As Jim F says above: anything that reduces heat is good imo..More O/C-ability :Big Grin:

 

EDIT: any real experts feel free to totally contradict anything and everything I've said - as I say, I'm not an expert!!

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Now that I know my processor DOES NOT HAVE HT :blush: and that FLIGHT nonetheless runs smooth as silk on it, I am about to go flying to Georgia, using a top-notch-ultra-detailled p-51 that was programmed to get real use of it... and one I am sure I can easily fall in love for ..... Well, I've been desperately resisting it, but I don't know if I can stand it much longer... Then I will probably find out I should better have done the homework and invested on an HT-ready processor :-(

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Then I will probably find out I should better have done the homework and invested on an HT-ready processor

 

Hello

HT is of little use other than to generate more heat, you will not miss it.

On the other hand getting a K series chip and pushing it above 4.6 ghz makes a real difference, more than HT ever will, that is where the homework would have proved useful

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On the other hand getting a K series

 

Mine has no 'K' on the name, I believe, so, although I do not intend to play OC right away (it's very hot already here in Lisbon :-) ) I might give it a try, but, will the 2500 handle it?

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