Hyperthreading

[Bobsk8 12,677]

Does P3D use hyperthreading, in other words would an i7 run P3D better than an i% because of the hyperthreading capability? 

[Bert Pieke 7,584]

It is not a matter of "using HT" but getting increased performance with HT.

 

I believe it "uses" HT, just like FSX does, but most users get little to no value

out of that capability.

[TurboKen 221]

You are better off leaving HT-OFF and raising your overclock. For example you may overclock to 4.6 but with HT- ON with the increased heat you may only get 4.3/4.4 stable.

 

I had a 2600k that would be happy all day @ 4.8, so I left HT- Off as I saw no difference with any testing I tried. But if you already have an i-7 go ahead and try it, see what works for you.

[vgbaron 3,597]

There's some good info from Steve Waite in here - I switched to HT on and have smoother operation.

 

 

 

http://www.avsim.com/topic/468195-p3d-and-hyperthreading/

 

 

Vic

[DylanM 1,069]

Unlike FSX, you should be able to see benefits in terrain paging with HT on (and potentially improved smoothness).

 

See what overclock you can push to with HT enabled, and give it a try on and off. 

[pmanhart 176]

You are better off leaving HT-OFF and raising your overclock. For example you may overclock to 4.6 but with HT- ON with the increased heat you may only get 4.3/4.4 stable.

 

I had a 2600k that would be happy all day @ 4.8, so I left HT- Off as I saw no difference with any testing I tried. But if you already have an i-7 go ahead and try it, see what works for you.

 

I believe this wisdom hasn't applied to the Haswell line (and assuming the Skylake line as well), but did apply to everything Sandy/Ivy-Bridge.

[angeli662 43]

I thought FSX has not been coded to use HT if so P3D should be the same. Here is a quote from another site.

 

 "Intel Hyper Threading: FSX has no code to recognize or process logical core hyper thread. I don't know how many times I have read some 'guru' has come up with an assessment that FSX will make use of or runs better with hyper thread enabled. This person really needs a sign! The REAL terrain 'guru' Adam from Aces as well as Phil Taylor specified years ago that FSX does not support any logical core threading (hyper thread).

 

The reason you SEE logical core activity in the Windows CPU monitor window is because the physical cache is used for each logical (hyper thread) core. "logical" core means there is no 'physical' hardware core but the hardware cache in use is there, and, FSX is DUMB so a thread is spawned due to the physical cache in use, but the data is never processed and used by FSX!"

[jabloomf1230 2,445]

The HT is invisible to both FSX and P3d. FSX is only weakly multithreaded and only accesses a limited number of cores, whether physical or virtual. P3d will access as many cores as are available. For example, I have a dual Xeon system, with each processor having 6 physical  cores. I run with HT off, because there is no real advantage to HT, but with HT on, P3d uses all 24 "cores". It really doesn't help performance that much, because in P3d most of the CPU cores only load scenery.

[SteveW 1,792]

FSX doesn't "use hyperthreading" and knows nothing about it, neither does P3D. In a nutshell, HT increases the efficiency of thread swapping on a core. It comes with a price, 2 logical processors per core sharing the throughput of that core. Because of that some apps may spawn threads that start up on LPs shared by the same core and so compete on that core for maximum throughput. Apps that might do that can be helped to avoid it with an Affinity Mask that moves on the next starting thread to the next core by blocking an LP of the first core. Some apps, FSX-SE for example, spawn threads that don't compete on an HT enabled system and don't need an AM. FSX and P3D spawn upwards of 40 threads, from the use of a multitude of system resources like networking and IO. HT enabled systems increase efficiency of handling many threads greatly, else it wouldn't exist. However, with the cost of extra HT hardware on chip, in terms of heat, there may be a trade off with HT disabled when looking for ultimate GHz. Even though FSX doesn't use HT, it's running on a system that can find benefit from HT and can improve performance of the sim overall.
 

[G MIDY 101]

HT should always be off to allow for the highest, stable overclock unless an application specifically will use it. A higher overclock will always yield better performance in P3D/FSX because more processor cycles means more work can get done. HT allows for better multi-tasking but ultimately no matter how many threads exist, the processor can only do so much per cycle - HT doesn't change performance the same increasing the amount of memory doesn't.

[WarpD 824]

As Prepar3D moves further and further away from being CPU bound... this thread's posts are a plentitude of misinformation. Prepar3D v2.x and most especially v2.5 do extremely well with HT enabled.

 

This isn't FSX. Using FSX as an explanation for anything when discussing Prepar3D is of little value.

[angeli662 43]

As Prepar3D moves further and further away from being CPU bound... this thread's posts are a plentitude of misinformation. Prepar3D v2.x and most especially v2.5 do extremely well with HT enabled.

 

This isn't FSX. Using FSX as an explanation for anything when discussing Prepar3D is of little value.

I am glad to know the P3D has been recoded  to use HT, maybe I  should give a try,  my system with HT would give 16 cores.

Unfortunately my FSX-SE causes my main PC to crash with HT enabled it doesn't like it at all.

[WarpD 824]

Actually it's probably your overclocking that's the source of the crash, but you probably don't want to hear that.

[DylanM 1,069]

As Prepar3D moves further and further away from being CPU bound... this thread's posts are a plentitude of misinformation. Prepar3D v2.x and most especially v2.5 do extremely well with HT enabled.

 

This isn't FSX. Using FSX as an explanation for anything when discussing Prepar3D is of little value.

+100.

[angeli662 43]

Actually it's probably your overclocking that's the source of the crash, but you probably don't want to hear that.

I do want to hear all the info I can get :smile:  I think is part of the fun to try new setting. my OC has been solid for a long time, HT + my FSX not so good. Very curious to see if P3D  would do in my system with HT enable.