Last summer I built and configured a FSX system after advice from Nick and his bible. One advice was to disable HT since FSX can't benefit from it. But I have now P3D2

which I think can use HT. On the other hand I think enabling HT will make the CPU run hotter so maybe I must lower my current 4.5 GHz OC? The same questions would also apply if I would get XPLane 10. So what is the best thing to do here? What have you done?

Your CPU will be 10 degrees hotter with HT on. So you will have to determine if +10 degrees pushes your CPU above the temp you are happy with.

 

I've no idea if P3D2 enables FSX to utilise HT. I doubt it.

Your CPU will be 10 degrees hotter with HT on. So you will have to determine if +10 degrees pushes your CPU above the temp you are happy with.

 

I've no idea if P3D2 enables FSX to utilise HT. I doubt it.

 

Actually when I tried enabling HT my registered temperatures were no different than they were before (67 C). And I didn't noticed any improved performance in P3D2. But that was no thorough test.

FSX is making use of hyperthreading for texture loading. I use it all the time for photo scenery with high LOD setting. And yes I can both see and also messure an actual difference. I know what Nick says, but he is not right in this case saying that FSX cant benefit from Hyperthreading. It's just in particular cases it shows. It doesn't give you more FPS though, but that is just as Microsoft intended it to work unfortunatly. It does however also drive up the temperatures. You have to tweak the AffinityMask setting accordingly as well as if you dont have an AffinityMask entry in your cfg FSX won't make full use of the extra threads provided as the default AffinityMask 'ignores' them as the Hyper Threaded CPUs availible when FSX was coded were only single core + very few $1200 Pentium Extreme Edition dual core ones. Those types of CPUs work fine with the default affinity mask behaviour but its not optimised for hyperthreaded quadcore (or higher) CPUs. As the default affinity mask won't create more work when you activate hyperthreading the CPU temps won't go up than either until you tweak the affinitymask setting.

 

I don't know what extra (if any) work that has been multi threaded with P3D2 but I do know that FSX uses multi threading for batching autogen. I also know that P3D2 now batches autogen way further out compared to FSX. Any recent dual core CPU without hyper threading was able to keep up with maximum autogen saturation in FSX  though so hyperthreading was never needed to help with it. Couldn't tell if it would be helpful for autogen in P3D2 as I've never used it, and I dont know if there ever is an issue to keep maximum autogen saturation with it. Don't even know how default AffinityMask behaves when using Hyperthreading with P3D2 but I do know that default AffinityMask for a non hyperthreaded CPU changed compared to FSX.

My highest OC at 4.8Ghz is only stable with HT on, that said, heat is not really an issue with my case of several 140mm fans pushing the hot air outside the room via pipe.

 

The room does not heat up, PC has endless supply of cooler air inside the room, so HT on and heat no issue here.

HT is not an issue with heat if your running a decent water cooler - I dont know otherwise as I have always run a water cooler - I would turn HT on

 

HT is mostly for overall system performance - not just FSX in play here

In theory HT is more efficient for multiple threads in Windows apps - that's what it was designed to do and why it exists today. Even though the HT disabled CPU would have to do more work for the same set of multiple threads, temperatures would work out more or less the same, but the HT disabled CPU would be slower.

"In theory HT is more efficient for multiple threads in Windows apps - that's what it was designed to do and why it exists today. Even though the HT disabled CPU would have to do more work for the same set of multiple threads, temperatures would work out more or less the same, but the HT disabled CPU would be slower. "

 

And spoken from the true Master   :drinks: 

The Windows core subsystems like networking respond healthily to HT enabled and FSX/P3D make a lot of use of that. HT is kind of a stop gap while CPU architectures are sorted out, and probably will be phased out with more advanced designs. There is a possibility of higher temps with HT enabled but it's just doing more work, avoiding that to OC higher can be counter productive.

 

Thanks for making me blush Rich.

"Thanks for making me blush Rich."

 

Same thing happens to me when you throw out all this excellent knowledge Mate   :im Not Worthy: 

There is a possibility of higher temps with HT enabled but it's just doing more work, avoiding that to OC higher can be counter productive.

In my case...

 

i7920, HT on equated to 10 degrees higher CPU temp. No discernible difference with HT on in FSX.

 

i7 3770K, HT on equated to 9 degrees higher CPU temp. No discernible difference with HT on in FSX.

 

In my case, 10 degrees lower CPU temp, and thus more overclocking latitude is therefore preferable.

I presume the extra heat from HT enabled, comes from running two or more threads more efficiently - if it gets hotter it's doing more work, right? In my case with HT disabled there is not a performance improvement, for example dense overcast conditions clearly hit fps in an obvious way with disabled HT. (I'm saying at first glance all seemed the same with HT disabled, but later something shows up)

All tests I have done to date show no benefit for me, "with my set-up" with HT on. I'll do some test if I get the chance though, and pay attention to dense overcast as you say.

 

I did have a discussion a few weeks ago with someone, who claimed that HT is a minor advantage for photo scenery. I can't vouch for the veracity of that, as I don't have photo scenery.

4770K here at 4.3 and little difference temp wise between HT on or off.

 

gb.

When you say "little difference" what do you mean by that? What was the difference?

 

You should test under full load with a stress test and compare temps with HT on and off.

 

I would be surprised if the difference is much less than 10 degrees.