i7 Hyper Threading On?

[Papafox]

Hi all,
My i7 920 is working well, but I'm curious about what you think of turning off hyper-threading. Under load, my cpu runs cooler without hyper-threading, and I doubt that MSFS X gets much use out of the extra 4 threads. Your thoughts?

[NickN]

hyperthreading will only benefit applications that are hyperthread aware and make use of the tech

It will provide nothing for FSX

But if you video encode or use A/V software.. you want it on as it will make video crunching blazing fast

[macca22au]

Nick:  I recall that SP2 provides for some limited hyperthreading, and as I understand it, this is for some portion of the scenery textures.

It is minimal, but it is a little better than nothing.

On the other hand as you say, an SLI dual card is useless in FSX.

So I do permit hyperthreading although I know it is only the minimal amount that SP2 allows.   At least MS took some notice of the complaints that the hardware was a mile ahead of the very old coding of FSX and did a bit of recoding for SP2.

DX10 on the other hand is a great big fat nothing on SP2, even though some foolish people (ie me, converted to Vista in the belief that SP2 would bring a total DX10 experience in FSX, (sigh))

[NickN]

There is a difference between hyperthreading and 'physical cores'

Hyperthreading on i7 there are 8 threads in use for 4 cores

your not getting any more perf with hyperthread on (8 threads/4 cores) or hyperthread off 4 threads/2cores, 2 htreads. 1 core

FSX was made MULTICORE aware, not HYPERTHREAD aware

[raptorx]

With HT on I took a flight in NY city under full settings.

[dvpro]

How do you get all your cores to work so much...under full load in FSX I see MAX 45-50%....However I am not clocked yet....still waiting to find that one magical post that has very simple instructions on how to do it.

Anyhow, I was wondering about this too (HP) I do encode video...some HD but mostly SD video. I did a few test with this new rig and what took my old P4...20 minutes, took this new rig about 3 to complete....But I don't always edit...maybe a few hours per month...should I just skut down HT and only turn it back on when I am going to edit? Aside from FSX I use Adobe CS3 Master suite of programs...I ASSume they are HT capable...what say you?

[T1MT1M]

[quote]Nick:

[Slotback]

Let's not confuse the two.

Hyperthreading is where one core can be two logical processors, which in some tasks like encoding has massive gains. For example, my old Pentium 4 was hyperthreading, it had two logical cores, and as such, could run two threads; but that doesn't mean it's a dual core, it's only logic.

Multithreading is a programme that uses multiple threads, which takes advantage of multi core processors, and usually hyperthreading processors.


RTM FSX was pretty much single threaded. It ran on one core, or one logical core. Why was it single threaded? Because RTM FSX sucked.

SP1 / SP2 FSX will scale the scenery engine correctly up to a practically unlimited amount of cores. Multithreaded. My Q6600 routinely reaches 100% utilization on all cores in FSX SP1 / SP2, particularly when I'm flying fast over dense autogen.

In FSX SP1 and SP2, you could use a]the JOB SCHEDULER tweak, which could make the sim treat any processor as a 1, 2, 3, 4, 5.... 128, core processor. On my old Pentium 4, with SP1 and SP2, using a tweak to make FSX multithreaded to supposedly, 'take advantage' of Hyperthreading, had no gain. It created microstutters which just as not worth it. Enabling it caused, in my case, microstutters.

FSX is designed for multiple cores, not multiple logical cores. If you try and run it that way there will probably be no gain, and perhaps many problems.

So. You want Hyperthreading DISABLED. And NO jobscheduler tweaks in fsx.cfg.

[raptorx]

Let's not confuse the two.

Hyperthreading is where one core can be two logical processors, which in some tasks like encoding has massive gains. For example, my old Pentium 4 was hyperthreading, it had two logical cores, and as such, could run two threads; but that doesn't mean it's a dual core, it's only logic.

Multithreading is a programme that uses multiple threads, which takes advantage of multi core processors, and usually hyperthreading processors.


RTM FSX was pretty much single threaded. It ran on one core, or one logical core. Why was it single threaded? Because RTM FSX sucked.

SP1 / SP2 FSX will scale the scenery engine correctly up to a practically unlimited amount of cores. Multithreaded. My Q6600 routinely reaches 100% utilization on all cores in FSX SP1 / SP2, particularly when I'm flying fast over dense autogen.

In FSX SP1 and SP2, you could use a]the JOB SCHEDULER tweak, which could make the sim treat any processor as a 1, 2, 3, 4, 5.... 128, core processor. On my old Pentium 4, with SP1 and SP2, using a tweak to make FSX multithreaded to supposedly, 'take advantage' of Hyperthreading, had no gain. It created microstutters which just as not worth it. Enabling it caused, in my case, microstutters.

FSX is designed for multiple cores, not multiple logical cores. If you try and run it that way there will probably be no gain, and perhaps many problems.

So. You want Hyperthreading DISABLED. And NO jobscheduler tweaks in fsx.cfg.

There's some talk over at avsim about the core i7 Hyperthreading and setting the job scheduler affinity mask to 255.  So even though the task manager shows all 8 "cores" being used, that is offering no real gain?  

-Jim

[Slotback]

In my experience, no gain, only problems. I think Nick would agree.

[NickN]

Unless Intel has changed how hyperthread works and without it enabled only 1/2 of each physical core in i7 is being used, turning it on is netting the psychological result of seeing activity in the boxes.

It is my understanding that FSX SP2 is multicore aware, not hyperthread.

If you are at 4Ghz and on the fence with temps enabling the feature can throw you over the top on heat.

I usually find when things like this get posted the results are one person says they see a difference and another says they cant see a difference, and then another says they see a small change.. then another says the system runs worse.

In that, we have a tweak that does not exist but people will see what they want to see based on readouts, benchmark software and other visual aids that are giving the person what they want to see and its simply applied all the way through, or, the change is affecting an issue which could be resolved through other means bt had nothing to do with HT being enabled/disabled to begin with.


50% CPU use with HT off should not mean only 50% of the processor is being used

[NickN]

Ill tell ya what this reminds me of... VSYNC DISABLED

I can dig up thread after thread after thread where people SWEAR with Vsync disabled the sim ran higher frames and smoother

OF course it runs higher frames! Vsync locks the frames at the refresh rate of the monitor!

The psychological result of seeing the frame counter move over the refresh rate allowed all sorts of perfomance 'sightings' to occur

I will look at it again when I get time.. but nothing I saw here indicated HT was doing anything for FSX