Hypertherading

[jackieteh]

Hi all, i have a very stupid question here,

May i know how to turn off hyperthreading?

Regards,
jackie

[AshtonWoolley]

I think you have to enter your BIOS when booting your computer and there should be an option in there.

[Joelaff]

Yes, in the BIOS. See the manual for your motherboard.

However, most things these days are faster with it on, especially if you are on Win 8.1 (or interestingly XP64 for that matter). Win Vista and Win 7 both do not handle thread priorities properly for per-emptive multi-tasking. So rendering in the background can slow down your interaction, especially with HT on.

[jackieteh]

I think you have to enter your BIOS when booting your computer and there should be an option in there.

Thank you for reply

[jackieteh]

Yes, in the BIOS. See the manual for your motherboard.

However, most things these days are faster with it on, especially if you are on Win 8.1 (or interestingly XP64 for that matter). Win Vista and Win 7 both do not handle thread priorities properly for per-emptive multi-tasking. So rendering in the background can slow down your interaction, especially with HT on.

Thank you for reply, and it is really surprise that winxp working fine with HT, i will give it a try on my old winxp pc

[Joelaff]

What are you trying to achieve by turning it off?

You can set VRay to use low thread priority in the settings. This still slows things down a little on Vista or Win 7. You can go to the task manager and adjust the processor affinity, free up one whole core (two HT threads). However, this is less optimum than threading that works properly, where the FG process always gets all the resources it needs, regardless of what is running in the background. Win 8.1 is pretty close to this. I would not want a workstation running Win 7 after using 8.1 (with Classic Shell of course so you never have to see that Metro worthlessness). Note that even in 8.1 you need to make sure the priorities are set right (render low, FG apps either normal, or above normal if you want it a hint better). Note... Don't ever try setting something like a render to realtime. The mouse runs at realtime. You will end up having to force reboot. Don't ask me how I know of course I haven't done that since XP, or maybe it was NT4.

[jackieteh]

What are you trying to achieve by turning it off?

You can set VRay to use low thread priority in the settings. This still slows things down a little on Vista or Win 7. You can go to the task manager and adjust the processor affinity, free up one whole core (two HT threads). However, this is less optimum than threading that works properly, where the FG process always gets all the resources it needs, regardless of what is running in the background. Win 8.1 is pretty close to this. I would not want a workstation running Win 7 after using 8.1 (with Classic Shell of course so you never have to see that Metro worthlessness). Note that even in 8.1 you need to make sure the priorities are set right (render low, FG apps either normal, or above normal if you want it a hint better). Note... Don't ever try setting something like a render to realtime. The mouse runs at realtime. You will end up having to force reboot. Don't ask me how I know of course I haven't done that since XP, or maybe it was NT4.

I am a win 7 user, and i read a thread from here regarding turn off the HT can speed up the DR render or something....
but from your reply, is it mean that i only need to set Vray to use low thread priority instead of turn off HT, am i right?

[super gnu]

leave HT on for vray... in ancient times (pentium 4 days) ht often used to be better left off.. for mental ray in particular. but these days its a nice boost. id be interested to see which thread you saw.

[Joelaff]

Yeah, if the goal is to render faster you definitely want HT on. If the goal is better interactivity while doing something (like rendering) in the background then it is possible HT off will be more responsive. However, it will slow down your renders. Best performances comes with Win 8.1 64bit and HT on.

[Morne]

A while back there was issues with HT and machines with a HIGH THREAD count like 64. HT off was faster for those machines.
But that was a while back and I think Vlado already fixed the HT issue for machines with high number of cores

[jackieteh]

Thank you everyone for the clear explanation.