Hyperthreading - and Stuttering

[dburne 2]

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...

[WarpD 824]

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.

[dburne 2]

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.

[Illegitimi non carborundum 4]

Edit - wrong forum - apologies

[jandjfrench 3]

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.

[jimh425 0]

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.

[Guest]

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!

[jcomm 5,890]

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 ????

[Guest]

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...

[jcomm 5,890]

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!!!! :-)

[dburne 2]

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!

[jimh425 0]

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. ;)

[jcomm 5,890]

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

[n4gix 4,947]

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:

[Glynn 405]

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