The improvement in performance gained by the use of a multi-core processor depends on the APS software algorithm and the fraction of software that is parallized to run on multiple cores simultaneously. For FSX, performance gains from quad core processors and beyond are dependent on what algorytms are included in FSX SP1 and SP2.

For my i7-920 I have been successful in stabilizing all four cores to provide, under load, approximately the same or equal level of CPU usage and performance from each of its cores. As a result I can obtain smooth flights anywhere in the world with good frame rates. For example, look at the following two screen shots with Task Manager usage displayed of a P51 Mustang flying directly over Manhatton. I picked this location as it is one of the most intensive performance killer for FSX with its thousands of buildings and surrounded by three large airports. My frame rate for the first screen shot is 33.1 and the second 27.2. I get even better performance over JFK.

This first screen is looking from outside the aircraft down on Manhattan with total CPU usage at 40 percent.



This second screen is a cockpit view with total CPU usage increased to 55 percent and spread equally over all four cores.



As I have indicated in previous postings I keep my FSX flight settings taylored (maxed out)for this PC. It stays this way for all flights. And I use FSGenesis, Megascenery, Ultimate Airport, REX, GEX, UTX, and more.

Now from what I have learned through research the last few weeks, it would not make sense for me to upgrade my CPU as it still has not utilized its full potential at 4GHz for FSX. And I don't think that going to 5GHz, which was my earlier target, will visually provide a difference (yes faster for other applications but not noticeable in FSX. However, upgrading my GTX 285 to a GTX 480 significantly increasing the on board memory and processing cores may provide an improved photogenic display and possibly a few more FPS.

There is a question that I have not been able to get a good answer and that is how well does a six core processor run FSX? Does the two additional cores make that much of a difference? Especially since there has been no upgrades for FSX since SP2 and none to be expected. And,

If any one should ask, I only use three tweaks in my fsx CFG.

1. FIBER_FRAME_TIME_FRACTION=0.20

The default setting for this is 0.33. This is the CPU time FSX devotes to loading scenery and textures. This variable determines the amount of CPU time given to loading scenery as a fraction of the time spent in rendering.

2. [JobScheduler]
    AffinityMask=14

A setting of 14 changes core 0 to run only the fibers resulting in a more equal load across the remaining physical cores.

3. [BufferPools]
    PoolSize=500

This, for me, ensures for a smooth flight.

Quote:


Overkill Beyond Overkill (Did you just change your name?)

By rules of the forum, I must reduce the size of the screens to 155 kilo-bytes and if I disabled hyper-threading I would lose my overclock. So the two screens I am showing you include graphs from both Core Temp as well as Task Manager so you can compare the results. And since they will be hard to read, I am typing the results for you.

This first screen is from inside the cockpit directly over Manhattan. The Task Manager graph shows the CPU Usage at 55% and equally spread across the four cores. In comparison, the Core Temp graph shows the percent of use for each of the four cores, 0=52%, 1=59%, 2=57%, and 3=49%. The average for the four cores is 54.3% as compared to 55% for the Task Manager. The FPS for this screen is 24.3 FPS.



This second screen is from outside the P51 showing it directly over Manhattan. The Task Manager graph shows the CPU usage at 52% and equally spread across the four cores. In comparison, the Core Temp graph shows the percent of use for each of the four cores, 0=51%, 1=59%, 2=55%, and 3=56%. The average for the four cores is 55.2% as compared to 52% for the Task Manager. The FPS for this screen is 29.4 FPS.



The above results indicate to me that the Windows Task Manager and the Core Temp usage results are both very close with negligible differences.

What appears to me happening is that the FSX SW APS do not spread the CPU usage equally across 8 threads at the same time. I believe that they first address simultaniously threads 1,3,5, and 7, and then at some point when usage approaces or reaches 100%, then threads 2,4,6, and 8 are simultaneouly added to further boost core use. And remember, this is only my opinion.

Regards,

Flight Ace

flight
Ace, I like your persistence in looking for more performance. Reminds me of myself not long ago. I am going to look at your tweaks minus the Buffpools, I do not need that with the 480 anymore. According to people who know much more than myself,hyperthreading has no use in FSX. Skip

bunky wrote on Sep 18^th, 2011 at 10:12am:


Ground Hog,

I am always looking for new ways to improve FSX performance

I noticed that initally your motherboard and GPU (Asus P6td DELUXE,  EVGA 285) were the same as mine. You mentioned in your post that you now have a GTX 480. Also, our overclocks are close, yours 4.2 GHz and mine 4.0. May I ask what kind of a boost for FSX you experienced from your upgrade to a 480?

Regards,

Flight Ace

This isn't completely on topic, but how many cores can FSX actually use?

Phil Taylor is quoted saying that "FSX will scale up to 256 cores".

I have a question regarding multi core CPU's
Could I expect a noticable improvement in frame rates replacing a CORE 2    3.0Ghz 4mb L2 cache cpu with a
QUAD core 2.5GHz (slower than the core 2) 4mb L2 cache CPU?
I have checked the 'passmark' values (core 2 cpu is 1926
quad core cpu is 3550) which suggests that the quad core is more than 50% faster than the Core 2. But would FSX run noticably faster?