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ivo09

P3D and hyperthreading

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I have a 3570k in my system and I have sort of inherited another PC which has a 3770k. So I am thinking about swapping the chips and putting the 3770k in my PC. Does hyperthreading make a [performance] difference in P3Dv2.5 or am I better off sticking with the 3570k I have currently?

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Ivo, If you can overclock to the same speed and keep HT enabled, I'd say do it. P3D does take advantage of HT particularly for terrain paging. 

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I have a 3570k in my system and I have sort of inherited another PC which has a 3770k. So I am thinking about swapping the chips and putting the 3770k in my PC. Does hyperthreading make a [performance] difference in P3Dv2.5 or am I better off sticking with the 3570k I have currently?

 

Your current cpu - try HT on with Affinity Mask=84 - works great but I do have a 4.6ghz OC 

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Your current cpu - try HT on with Affinity Mask=84 - works great but I do have a 4.6ghz OC 

+1

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Turning ht=off on my cpu (i7 4790k) result in 4-5 fps increase but much worse texture loading even with tessellation maxed.

No cfg AM setting (84 gives very bad result to me) and sometime i turn off core 0 in taskmanager and enable it again in very busy sceneries (otherwise it is not necessary).

Ht works fine

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AM 84 gives very bad result to me

You do know thats  only when you have HT ON?

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Yes, of course. I said i'm using ht=on.

 

With ht=off am=14 gives an even worse result.

 

Gpu is ati r9 270x oc 1.250mhz, maybe it needs more cpu assistance to load the scenery properly.

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Good your post seems a lot clear'er than the last time I read it :)

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On my 5930K @4.7 Ghz (12 threads with HT enabled), I'm getting better results with no AM setting in the cfg.

 

Ivo, as you can see, getting the best out of setting AM in the p3d.cfg is very specific to the hardware you're running, so try both settings and see which one nets you better results.

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I also use no AM setting and no HT. Much better than using an AM.

 

 

Vic

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Thanks for all the replies. I think I will swap out the cpu since I'm going to install a new heat sink anyways. The 3570 is running at 4.6 so I hope to reach the same numbers with the 3770. I used to have AM 14 but I removed it and haven't noticed a difference.

 

Your current cpu - try HT on with Affinity Mask=84 - works great but I do have a 4.6ghz OC

Rich, I'm a little confused. I don't believe the 3570 has HT. Can you elaborate what you mean?

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Thanks for all the replies. I think I will swap out the cpu since I'm going to install a new heat sink anyways. The 3570 is running at 4.6 so I hope to reach the same numbers with the 3770. I used to have AM 14 but I removed it and haven't noticed a difference.

 

Rich, I'm a little confused. I don't believe the 3570 has HT. Can you elaborate what you mean?

 

I would swap cpu's but assumed your older chip being a K has HT - maybe not - have to look into but I would assume you all ready did - prepare to rebuild that system as the cpu switch will warrant that

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Actually it looks like a straight swap, the (i5)3570k and the (i7)3770k both use the LGA1155 socket. The only difference between the two is the HT on the 3770. I believe that in FSX it was recommended to turn HT off because it didn't help. Hopefully P3D can take use of these new virtual cores. ^_^

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To simplify it, think of it like this. Take a single core CPU and run two threads on it. The two threads are alternately given a short period of time to run on the CPU. In order to slice up the time available to each thread, they are switched over. That is to say, the current thread is stopped, its results stored away, and the other thread reloaded and run for the next time period. Although even in HT mode the core ultimately runs two threads by task switching, HT exists because task switching is far less an overhead with it.

 

Now take an HT enabled core, there are two logical processors (LP), now the core can handle both those threads, one on each LP. The task switching overhead is reduced dramatically by extended circuitry on the CPU, which is disabled with HT=Off. So really we want HT enabled, P3D will spawn upward of forty threads on the CPU which require networking and other core resources.

 

With the latest FSX-SE, one thing it seems to do is avoid running its main thread and a secondary sim thread on one HT enabled core. This app specifically places its threads logically. What we can do with P3D (and FSX) with an HT enabled CPU is apply an affinity mask to avoid the 'ganging up' of the primary sim thread with another on one core. So for example with a 4 core, 8LP (HT=On) CPU, we can apply a mask of 254=(11,11,11,10) which disables the first LP (on the right) so that the first sim thread runs on the second LP of the first core, but then the second sim thread moves along by one LP, on to the second core, and runs up on the third LP. So in short we apply a mask in HT enabled, but otherwise it's not an issue, unless we have many cores and we are in a position to partition the CPU among apps.

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