What is HT and what is it for?

[shaned]

I see people saying they have HT enabled or disabled. I looked in the BIOS and cant find it. What is it? What does it do and should I enable it?

[Chike]

Re: What is HT and what is it for?

HT is an abreviation for Hyper-Threading.
For some odd reason Award Software chose to use CPU Multi-Threading, and verious manuals descriptions are pretty much bogus.

[shaned]

Re: What is HT and what is it for?

So your saying hyper threading is the same as CPU multi threading? Should it be enabled or disabled? Whats the difference?

[Chike]

Re: What is HT and what is it for?

As I said documentaion is bogus. If you have 8 CPUs(in Task Manager performance tab) when enabled and 4 when disabled than yes this is Hyper-Threading.
My CPU does not support Hyper-Threading Technology and my BIOS does not have that option so I cannot tell you for certain.

[Nickel020]

Re: What is HT and what is it for?

Most games benefit from it actually being off. I would therefore switch it off for gaming. It generally provides a performance advantage in applications that are designed to take advantage of more than 4 CPU cores. Most games do not do that though, and they actually take a performance hit from it.

Intel's current official name is actually SMT - Simultaneous Multi-Threading.

[ell]

Re: What is HT and what is it for?

Most games benefit from it actually being off. I would therefore switch it off for gaming. It generally provides a performance advantage in applications that are designed to take advantage of more than 4 CPU cores. Most games do not do that though, and they actually take a performance hit from it.

Intel's current official name is actually SMT - Simultaneous Multi-Threading.

I don't necessarily agree with you, your saying games take a hit as if its significant or noticeable (marginal differences shouldn't be used as a reason to disable it), I recommend you keep it on, as you can expect a better multitasking experience, I use it and i have notice certain applications that take advantage of it. of course I'm not going to sit here and measure minute differences, but intel implemented these for a reason so software can take advantage of them.

[genec57]

Re: What is HT and what is it for?

I can get a stable oc of 4410 with ht off. The best I can safely do with ht on is 4200. All the evidence I have been able to accrue tells me that any benefit gained from ht is marginal at best.
The extra 200megahertz of clock speed IMHO well offsets any performance lost from disabling HT.
I think that will change in the future as more apps are written to take advantage of multiple cores. In the meanwhile I will settle for a mere four :).

[dbee]

Re: What is HT and what is it for?

I keep it disabled, saves me about 8c on average . check this short article out real quick, looks interesting...

The Frostbite 2 Game Engine For The Battlefield Series Might Go DirectX 11 - Legit Reviews

[dbee]

Re: What is HT and what is it for?

and from what i've seen , video encoding and such take much less time to do the job with HT/MT/SMT whatever you may call it on.

[Ickk]

Re: What is HT and what is it for?

Hyper threading is usefull if you have a lot of apps open , if you only run 1 game then its not needed ... you loose about 5 fps with it enabled not a biggie . But gain hugley if you have a lot of apps open and running , sever apps for instance.

To simplify
Each app you have open is alocated 1 of your cores if you have 2 cores then you open 3 apps you get pauses as each apps thread gets a timer on core use.

with HT you get addition virtual cores , suppose your app is only using 20% of core 1 ... with HT that not used 80% can be given, allocated to another apps thread.

[dbee]

Re: What is HT and what is it for?

I actually did a test last nite , doing a full scan with Kaspersky 9.0 First test HT was off and it took about 15 minutes to get to 10% . I cancelled it, rebooted with HT ON and started a new full scan. about 30 seconds in, im at 10%. ... Dont know if kaspersky already recognized the previously scanned files or what. But i really dont think HT can do something that big.

That link i showed above is for the FROSTBITE 2 engine which is designed to use anywhere from 2-8 cores/threads simultaneously . This is the beginning.

[Chike]

Re: What is HT and what is it for?

The problem is memory. Memory is by far slower than the CPU. Running a single thread on a single core results at times where there is no available instructions+data to feed the ALUs and the core doing nothing while data is being fethed.
With two excution threads that work on different memory areas this is less likely to happen, and the result is that the ALUs are always kept busy.
For any performance loss with HT enabled I would guess it is either Microsoft to blame or more likely the software that suffered performance loss.

[Ickk]

Re: What is HT and what is it for?

For any performance loss with HT enabled I would guess it is either Microsoft to blame or more likely the software that suffered performance loss.

I'm wondering if a thread is passed to a virtual core (HT), that HT core then wanted to do its work on a real real core thats busy or at 100% load. In this case a slow down results.

If this situation occurs ... i.m sure microsft has some HT manger that monitors real core usage and allocates the Hyper threads accordingly.

[Chike]

Re: What is HT and what is it for?

If this situation occurs ... i.m sure microsft has some HT manger that monitors real core usage and allocates the Hyper threads accordingly.

Exactly. HT is reccomended for HT awer OSs only.
I am quite sure Windows will favor diffrent physical cores before it will assign 2 processes to a virtual core.
But software has the ability to set affinity to a single or several processors and may prevent Windows from assigning a real core.

Still Intel is the last I'd suspect. They learned their leson with the FDIV bug.

[Psycho101]

Re: What is HT and what is it for?

With the coming of DX11 and it supposedly being extremely multi threaded, HT will no doubt be a boon to gamers. As it stands now, Nickel020 is correct with what he says. Having HT on can negatively effect gaming performance. It can do so anywhere from a tiny un noticable bit to a good chunk of FPS, depending on the game. If HT does happen to disagree with a game you're currently playing, then by all means disabling HT temporarily would be the correct thing to do, especially if you get HT caused dips below your comfort range for FPS.

I've used a 920 in Windows with both HT on and off. I have to say that personally I couldn't tell the difference. Windows GUI and most programs don't even use 4 cores as effectively as they could, let alone 8. The only time I noticed whas when running VirtualDub and a couple of transcoding apps. In tht case you'd be a fool to have HT off, as the performance results were sweet indeed!

It comes down to what you use the PC for. In all honesty, if you're a gamer, then a 1156 bsed PC or Even a 775 will be more than fine. Core i7 simply isn't needed in a gaming PC. The main reasons being that most PC games are ports of current console games or developed in unison and the fact that thet much CPU power just isn't needed yet (Hopefully in DX11 though). If Gaming only, I'd have HT off, save a few degrees c and maybe get a hiogher clock frequency (games srill scale with frequency on a i7, just not as much with the change in architecture IMO). If you run a work station and use multi threaded apps, DEFINITELY leave it on. If you run a wide range of stuff, leave it on initially and try it off too.