FSX and Multi-Core Processors

[Flight Ace]

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]

[Slotback]

Cool thread!

I have two requests though. Can you try doing the same thing, but this time with hyper-threading disabled in BIOS? And a higher resolution photo of this (not resized)?

Generally hyper-threading improves performance in the most multi-threaded programs by around 20%. I have a suspicion that if a application is not taking advantage of HT (FSX for example) yet the cores are in actuality all at 100% utilization, then task manager will erroneously show a CPU utilization of 50% which is a misleading result. I'm betting if you disable HT you will get the same performance in FSX yet task manager will show your CPU at close to or at 100% utilization which should be the correct reading. You can probably do the same thing without disabling HT by looking at CPU usage in programs like coretemp or throttlestop.

You could also try a program like MSI Afterburner which will show your GPU utilization and GPU memory usage during FSX. However, I think MSI Afterburner will only show the overall card utilization whereas some specific parts of the gpu core might be maxed out. i.e. the graphics card could still be a bottleneck at "40%" utilization.

I don't know how well FSX scales on hex cores and the like. At the end of the year I may purchase a 8-core system which will be overclocked at around 5ghz, but we'll see.

[Flight Ace]

Cool thread!

I have two requests though. Can you try doing the same thing, but this time with hyper-threading disabled in BIOS? And a higher resolution photo of this (not resized)?

Generally hyper-threading improves performance in the most multi-threaded programs by around 20%. I have a suspicion that if a application is not taking advantage of HT (FSX for example) yet the cores are in actuality all at 100% utilization, then task manager will erroneously show a CPU utilization of 50% which is a misleading result. I'm betting if you disable HT you will get the same performance in FSX yet task manager will show your CPU at close to or at 100% utilization which should be the correct reading. You can probably do the same thing without disabling HT by looking at CPU usage in programs like coretemp or throttlestop.

You could also try a program like MSI Afterburner which will show your GPU utilization and GPU memory usage during FSX. However, I think MSI Afterburner will only show the overall card utilization whereas some specific parts of the gpu core might be maxed out. i.e. the graphics card could still be a bottleneck at "40%" utilization.

I don't know how well FSX scales on hex cores and the like. At the end of the year I may purchase a 8-core system which will be overclocked at around 5ghz, but we'll see.

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

[Slotback]

I'm pretty certain that your CPU is bottle-necking you. It's hard to see in the pictures but it appears as if threads 1, 3, 5, and 7 are maxed out whereas 2, 4, 6 and 8 are at very low utilization. Remember hyper-threading (going from 4 threads to 8 threads on a quad) does not double performance, at most it improves performance by 30% in some specific applications. So if threads 1, 3, 5, and 7 are maxed out, then your CPU is in reality close to running at 100% utilization. This is reflected in your core temperatures of 70 degrees, which would be way too high for 50% utilization.

Disabling HT shouldn't affect your overclock at all.

If you change the affinity mask to 252 (makes the fibers run on all cores except for 1) then you can probably make all the threads be utilized but it won't improve performance.

[bunky]

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

[Flight Ace]

I'm pretty certain that your CPU is bottle-necking you. It's hard to see in the pictures but it appears as if threads 1, 3, 5, and 7 are maxed out whereas 2, 4, 6 and 8 are at very low utilization. Remember hyper-threading (going from 4 threads to 8 threads on a quad) does not double performance, at most it improves performance by 30% in some specific applications. So if threads 1, 3, 5, and 7 are maxed out, then your CPU is in reality close to running at 100% utilization. This is reflected in your core temperatures of 70 degrees, which would be way too high for 50% utilization.

Disabling HT shouldn't affect your overclock at all.

If you change the affinity mask to 252 (makes the fibers run on all cores except for 1) then you can probably make all the threads be utilized but it won't improve performance.

Based on your advise, I just disabled my HT and am finally getting believable readings from Core Temp and Task Manager. In fact, for the most part, my CPU, at times, does run at 100 percent in all four cores. So thank you.

All four cores at 100% with FPS at 24.9 over Manhattan


And you are right, my CPU is bottlenecking (inhibiting) me from improving performance. However, will flying better than 25 to 30 FPS matter? If I compare flights over Seattle, Manhattan, or the Los Angeles area with a flight in Rio DeJanerro, I see no difference in visual perception or picture quality. The difference is the numbers. Over Rio in some places I can exceed 100 FPS. Still looks and performs the same. So, for me, going to 5GHZ, is a challenge, not a necessity.

Still looking for some feedback on how well FSX runs with 6 core CPUs.

Flight Ace

[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

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

[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

Ground Hog,

I guess I am a little forgetful as I just recalled in a previous post, you already indicated that you got a nice boost in performance from upgrading your GTX 285 to a 480.
So just ignore my previous post.

Flight Ace

[F35LightningII]

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

[Flight Ace]

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

Four for sure, as I have had all four cores of my i7 920 utilized 100 percent. As for a six core processor, I really don't know as I am not sure how the SW was written for multiple processors running FSX. Was SP 1 & 2 written solely for the quad or to include all multi cores beyond the quad? Maybe someone out there who is currently using 6 cores running FSX can let us know how well they perform.

[Groundbound1]

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

[Slotback]

I think only the terrain engine scales up across multiple cores really well (as in, more than 4 cores). I think that means higher scenery settings can be enabled but I am not sure if it that necessarily translates into better actual performance since, as far as I know, the rest of the sim runs on only one thread.

Best ask someone who already has a hex.

[jparnold]

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?