Hi,Maybe I'm missing something, I thought FSX was unable to utilize Hyper-Threading and yet with it enabled via CMOS I get the following.

I dunno, but my quad core will use all four cores. I can watch the monitor as I fly if I'm in windowed mode.

FSX.exe itself probably doesn't, but any other software working in conjuction with FSX will probably use the other cores.Sounds like a reasonable explanation in theory...

The affinity mask tweak allows it to take more advantage of multiple cores.

Hi,This is a flight Sim only computer, all other utilities/addons (ActiveSky Evolution, WideClient, FSC, Radar Contact 4, Show Text) run on a separate computer.

FSX.exe itself probably doesn't, but any other software working in conjuction with FSX will probably use the other cores.Sounds like a reasonable explanation in theory...

Hi,So the AffinityMask of 255 is giving me eight threads and has nothing to do with Hyper Threading?.

The affinity mask tweak allows it to take more advantage of multiple cores.

Actually I didn't think that FSX >SP1 (ie SP2/Accel/Gold) actually needed the Affinity mask tweak: From: http://www.microsoft.com/games/pc/flightsimulatorx.aspx "Optimized for multi-core CPUs and improve draw times for faster loading" and P Taylor (see below) states,"Our multi-core support will take advantage of both 2 and 4 cores today, and more cores in the future when they become available via a config setting". I take that to mean that you would use a cfg setting ie Affinity Mask for say 6 or 8 core machines after all.I/m not sure about H-T, I haven't seen any change in my FSX install using H-T on or H-T off butFrom P Taylor: http://blogs.msdn.com/b/ptaylor/archive/2007/04/09/fsx-sp1-news-intel-quote.aspx"Note - hyperthreaded is not multi-core. Our current plan is to treat HT machines as single-core since we noticed extensive collisions between threads which caused stutters"RegardsPeterH

Hi Pete,If I remove the Affinity Mask tweak out of FSX's config file I end up with the following. So the AF Tweak is doing something and without Hyper Threading turned on I wouldn't have 12 threads.

Actually I didn't think that FSX >SP1 (ie SP2/Accel/Gold) actually needed the Affinity mask tweak: From: http://www.microsoft.com/games/pc/flightsimulatorx.aspx "Optimized for multi-core CPUs and improve draw times for faster loading" and P Taylor (see below) states,"Our multi-core support will take advantage of both 2 and 4 cores today, and more cores in the future when they become available via a config setting". I take that to mean that you would use a cfg setting ie Affinity Mask for say 6 or 8 core machines after all.I/m not sure about H-T, I haven't seen any change in my FSX install using H-T on or H-T off butFrom P Taylor: http://blogs.msdn.com/b/ptaylor/archive/2007/04/09/fsx-sp1-news-intel-quote.aspx"Note - hyperthreaded is not multi-core. Our current plan is to treat HT machines as single-core since we noticed extensive collisions between threads which caused stutters"RegardsPeterH

I don't think it's so much the HT threads wouldn't be utilized, as much as doing so won't increase performance. In fact it may actually diminish it a little, since the HT threads are virtual threads, so you're sharing the core speed of 1 physical core between 2 virtual cores.

Mike, do you notice any stuttering with ht turned on? I had turned off hyperthreading to get rid of stutters but I never tried it on and with a affinity mask tweak.

This has been stated along time ago that FSX is NOT hyperthread aware therefore it has no effect at all in FSX

Mike, that first graph is really interesting because it seems that everyone agrees that FSX can't use Hyper Threads.  Is there any noticeable difference in the game?Thanksjja 

Hi Jwenham,I know this has been discussed before and I was also under the impression that Hyper Threading was not possible with FSX, but how do you explain the first screen capture?This is an FSX ONLY machine, nothing else is running on the system. Yet eight threads are being used, you can see it in the screen capture. How is that possible if FSX is not hyper threading?If I stop FSX all eight threads return to idle.Isn't it true that Hyper Threading is transparent to the operating system and programs? If this is true and I have no reason to believe its not, then FSX does not have to be hyperthread aware as long as the operating system is capable of utilizing HT. Granted FSX may not take full advantage of Hyper Threading via its code but it should still see and use these additional threads.

This has been stated along time ago that FSX is NOT hyperthread aware therefore it has no effect at all in FSX

Hi jjjallen,I'm just getting ready to start testing with and without Hyper Threading as well as AffinityMask=255.

Mike, that first graph is really interesting because it seems that everyone agrees that FSX can't use Hyper Threads.  Is there any noticeable difference in the game?Thanksjja 

Thanks for testing this Mike :(

Hi tf51d,I understand that hyper-threading a processor will appear as two "logical" processors to the operating system, this should allow the operating system to schedule two processes simultaneously. I believe you may see a decrease in performance when two programs require all the CPU has to offer. However, I am not running anything on my system other than FSX so I should not suffer from this type of slowdown.

I don't think it's so much the HT threads wouldn't be utilized, as much as doing so won't increase performance. In fact it may actually diminish it a little, since the HT threads are virtual threads, so you're sharing the core speed of 1 physical core between 2 virtual cores.

...Isn't it true that Hyper Threading is transparent to the operating system and programs? If this is true and I have no reason to believe its not, then FSX does not have to be hyperthread aware....

Pretty sure that this is the case, when you use hyperthreading then you dont have any real cores. All your cores at this point are virtual "HT" cores, with two virtual cores sharing time on one physical core