I was reading a thread a few weeks ago about FSX and hyperthreading and it said that if you have an i7 and want to use all 8 threads then you have to do this:[JOBSCHEDULER]AffinityMask=255 Some people say it doesn't make FSX make use hyperthreading and it made no difference to them. I tried that setting and I noticed that textures load faster than before adding that setting on my i7 920 with hyperthreading on. Now I can make FSX actually run at a little higher frame rate than without hyperthreading turned on if I use this setting and lower the Fiber Frame Time Fraction setting where as before, hyperthreading would make FSX run a little slower on my PC. Am I going to have any problems with this tweak. I did experience a crash to the desktop when I was decending to Phoenix Sky Harbor but I'm not sure if it's because of this tweak.

With hyperthreading enabled, your system coul run FSX slower!Reason: HT throws off a lot of heat, so if you turn HT off, you could run the remaining "real" cores much faster by overclocking!Cheers,- jahman.

If the affinity mask is not specified, an application will run on all available processors. Thus setting an i7 affinity mask to 255 is the same as not setting it at all. I like to use HT with my i7 since I have other utilities running in the background while running FSX. It does generate lots of extra heat when OCed, but it's only a problem when running stress tests; with my FSX environment the temps usally top out at 66C for all four cores (measured with realtemp). I only OC to run FSX; all other times my rig is at 100% stock settings.

I read you, but the question remains: Is your FPS higher with HT at a lower clock due to heat. or without HT and thus a much higher clock.Try this and post back!Cheers,- jahman.

If the affinity mask is not specified, an application will run on all available processors. Thus setting an i7 affinity mask to 255 is the same as not setting it at all. I like to use HT with my i7 since I have other utilities running in the background while running FSX. It does generate lots of extra heat when OCed, but it's only a problem when running stress tests; with my FSX environment the temps usally top out at 66C for all four cores (measured with realtemp). I only OC to run FSX; all other times my rig is at 100% stock settings.

How do you overclock and then default clock on a whim of running FSX or not? How do you switch back and forth like that without making the bios changes, or do you do all that each time, and if so, why?

I've found that with my i7 860 I can't really get it to be stable past 3.8g and run a game regardless of whether HT is enabled or not, though I can run prime95 for hours. Seems that dagnabit on-chip pci-e controller is wreaking havoc. I've toyed with pci-e frequency with no luck, though I've yet to try higher voltages than 1.3V vcore and 1.15 QPI/Vtt since that is not where I want to go with this CPU. Overall I'm very happy with this OC and the associated gains with FSX performance.My Asus mobo has a 'save bios settings' where you can store up to 8 settings (which is an excellent tool for tuning up OCs); so when I want to run FSX, I reboot into the bios and load the OC settings (and restore them to stock when I'm done). I do this because this computer is the 'family computer' and I'd rather not have my wife and kids getting an out-of-the-blue BSOD and then hosing out the system with a sloppy reboot (been there and done that). Lately it has not crashed with my current OC settings, but why take the chance (especially when I'm at work). BTW, I get time for FSX only about 3 or 4 evenings a week if I'm lucky.

A lot of facts and testing here: http://forums1.avsim.net/index.php?showtopic=241915

Hi,i can't speak for FSX because i'm not in the mood for FSX and its problems at the moment.But recently i have enabled HT and undervolted my i7 920 because i saw improvements with other applications.There is a lot of text in the link which Ulf has provided and i haven't read everything but maybe the key for a successful use of HT is Windows 7.The thread scheduler of Windows 7 has been really improved (Idle Core and SMT parking). So maybe people want to test the use of HT with Win7 and FSX again.

Hi,i can't speak for FSX because i'm not in the mood for FSX and its problems at the moment.But recently i have enabled HT and undervolted my i7 920 because i saw improvements with other applications.There is a lot of text in the link which Ulf has provided and i haven't read everything but maybe the key for a successful use of HT is Windows 7.The thread scheduler of Windows 7 has been really improved (Idle Core and SMT parking). So maybe people want to test the use of HT with Win7 and FSX again.

I use an I7-920 @ 4.4Ghz/12GB ram on Win7-64 with HT=on and have tested it with HT=off and there is no loss or gain in FSX what so ever as logged in a canned flight using Fraps, no sharpening of textures, nothing to see that suggest it like you would see an applications that do actually use it.AffinityM does not change anything to enable or disableit over the default SP2 other then ther false report you might get in task manager and that is not the best tool to use. FSX was design to use up to 32 physical cores but was not designed to use HT.

I use an I7-920 @ 4.4Ghz/12GB ram on Win7-64 with HT=on and have tested it with HT=off and there is no loss or gain in FSX what so ever as logged in a canned flight using Fraps, no sharpening of textures, nothing to see that suggest it like you would see an applications that do actually use it.AffinityM does not change anything to enable or disableit over the default SP2 other then ther false report you might get in task manager and that is not the best tool to use. FSX was design to use up to 32 physical cores but was not designed to use HT.

I haven't tested it with FSX, i did just notice that the most posters wrote about WinXP and Vista, so i thought about the very few improvements of Win7 and maybe they are the reason why you don't even get negative effects like some have reported who have HT enabled.4,4GHz and HT on?? What temps do you get while running prime95 and what cooling-system and voltage settings do you use?EDIT:stupid question: how is an application like FSX able to distinguish between logical and physical cores?

Phil Taylor: "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."source: click:(http://www.youtube.com/watch?v=Bmk9CjEha8A...feature=related

stupid question: how is an application like FSX able to distinguish between logical and physical cores?

Application can access basic (identification) parameters of a CPU.

I always thought that the application would only be able to see the logical cores and only the OS would schedule the threads. On multi-core CPUs with HT, the OS would first assign the threads on the physical cores, so there wouldn't be the collisions between two threads which they had seen with single core CPUs.

After reading the above link on the FSX affinity mask and running some experiments, my earlier comment on an affinity mask of 255 is equivalent to not setting one is incorrect when in comes to FSX.cnfg (but in general use it is true). Seems to me that without any affinity mask setting, FSX can determine what CPU resources are available and utilize them such that it will use all the available physical cores and seemingly ignore the logical ones. If an affinity mask is specified, it will use all cores specified by the mask whether they are logical or not. I've found that my HT enabled i7 860 likes an affinity mask of 85 (only physical cores) over none at all, mainly in that it runs a bit cooler (62c vs 66c) and maybe a bit smoother (though IMO FSX smoothness seems to vary with phase of moon). I've seen my HT OC overheat (up to 85c) in a few minutes when I run prime95 stress tests on all 8 'cores', so I'm know I on dangerous ground with HT enabled. Whatever...enjoy, TFM.

I use an I7-920 @ 4.4Ghz/12GB ram on Win7-64 with HT=on and have tested it with HT=off and there is no loss or gain in FSX what so ever as logged in a canned flight using Fraps, no sharpening of textures, nothing to see that suggest it like you would see an applications that do actually use it.AffinityM does not change anything to enable or disableit over the default SP2 other then ther false report you might get in task manager and that is not the best tool to use. FSX was design to use up to 32 physical cores but was not designed to use HT.

You are correct sir! 980x 4.5oc watercooled and no change in frames with ht on or off.Joseph Blair