Virtual Cores On or Off?

[Joss]

This is about simultaneous multithreading in general, so both Intel and AMD.
I've been watching several videos and reading tests and although the results are somewhat mixed I have the feeling that with higher (physical) core count, 6 and above, turning multithreading off can be beneficial in gaming.
What are your opinions and experiences with this? Did you do your own testing? Do you game with multithreading on or off?

 

[Vayra86]

Minor if not negligible FPS boost in a very small selection of games, but a potential major FPS boost and min. FPS advantage in many others.

Keep it on. If you have stuff running in background, HT and SMT always improve performance. We are now actually reaching a point where devs are making better use of it too (both physical and virtual cores that is).

Its correct though, results are mixed, and hard to trust. The use of threads is almost unique per use case and even for each point in time. Why - because Win 10 for example has a tendency to do things on its own, and so do other apps, and because people tend to have several active applications alongside a game running, like a browser, but also things like Steam Overlay etc.

 

[27MaD]

Yes , enable it , why keeping it disabled?

 

[HD64G]

Modern games use it as it should and helps. Old ones might have problems but more often than not it is beneficial. Older Intel CPUs (i7 920 gen mainly) had more of a problem using it properly back then but I guess with windows 7, 8.1 or 10 the os utilise HT better than when they came out. Now, from a security perspective some newfould flaws are helped by HT to penetrate. Double edge knife.

 

[Mussels]

its all over the place if it helps or hinders, but a basic rule of thumb would be the more modern the hardware and more modern the software, the more beneficial it is

The main times it ever helped was thermally limited hardware, that would boost higher/sustain higher base clocks without the added heat (think laptops with crap cooling, or a stock cooler filled with dust)

 

[RejZoR]

I've had HT enabled CPU for over a decade and not once I felt the need to disable HT in order to have a "boost" in games. They just all run super smoothly. Whenever I disabled it, it just ran worse.

 

[newtekie1]

I've had HT enabled CPU for over a decade and not once I felt the need to disable HT in order to have a "boost" in games. They just all run super smoothly. Whenever I disabled it, it just ran worse.

Yep, same here.

In fact, in at least one case having HT enabled made a game playable that was 100% not playable without HT.

 

[cadaveca]

What are your opinions and experiences with this? Did you do your own testing? Do you game with multithreading on or off?

The cores aren't "virtual". What happens is that each core has a singular FPU processing unit, some capable of 512-bit operations these days, that gets shared between the cores (usually fused 256-bit). The other parts of the CPU core are duplicated. These FPUs are capable of multiple operations packed into that 512-bit goodness. That's why there are "virtual" cores... they help pack those FPUs with data so they don't go wasted.

 

[Bill_Bright]

I just don't understand why folks keep thinking changing the defaults is better. It rarely ever is. For the normal user, and that's all of us between 2 and 99% of the users out there, the defaults are the best setting for our systems. And note many of those settings are "dynamic". That is, when the motherboard BIOS and OS detect specific connected devices, hardware configurations and installed software, the BIOS and OS "dynamically" tweak the settings for us! That's a really good thing!

That's why the default settings are set the way they are. The hardware makers sure don't want to stifle performance. That would create bad press! The game makers don't want to stifle performance. And the OS makers don't want to stifle performance either. So why would they? ???

To you specifically, Joss, I doubt seriously any of the 81,513 members of this site have a computer setup exactly like yours. So I am 100% certain your computer is unique. Only you have that exact same CPU, motherboard, RAM, graphics, drives, network connection and operating system combination. And only you have your OS setup exactly the way you do. Nor does any user on this site run the exact same programs or use their computer in the exact same way as you do.

What does that mean? It means only you can determine if changing a default setting is better or worse for the tasks you perform on your computer. So I say, try it and see. Then let us know what you discovered. Just be aware of the placebo effect. It can influence even the best intentions and distort perceptions of even the most open-minded professionals.

 

[robot zombie]

I always thought it was best to leave it enabled if you have it. Turning them off isnt the same as not having them. If anything turning it off hurts performance ime.

 

[btb]

Basically its a non-issue, since its the graphic card that is by far the most important factor when it comes to FPS in games.

But my own personal preference is definitely towards only having "real" cores. That way you can avoid any potential issues with games where they might try to schedule too many threads on what the engine thinks is a real core, but in reality is a shared core, and end up hurting performance. In this video you can see several examples where the FPS with hyperthreading on is actually lower than with hyperthreading disabled(edit: fixed typo):

 

[Caring1]

….the FPS with hyperthreading on is actually lower than with hyperthreading enabled....

 

[John Naylor]

This is not an either or thing .... back in 2011 (Sandy Bridge) , when I built my youngest son's box, read a review that tested on/ off and ON was 7C hotter. So, what I did was I got up to 4.6 GHz w/ HT on and i saved the BIOS settings as profile 46 ... I then turned HT off and tweaked and was able to get to 4.8 GHz at the same temps. But even at the same 4.6.... many games were a few fps faster w/ HT off. Anyway, I saved that BIOS profile as "Profile48". So when ya boot the machine, you can just hit delete key to get into BIOS select slot 3 (profile 46) or 4 (Profile 48) and play w/ it ON or OFF as you see fit ... that particular day.

It was a fun and enlightening investigation ... not so much tho that i wanted to repeat it as yet. Like RAID, it's something I just "gotta try" every cupla years but haven't as yet had the urge.

 

[Disparia]

Turned it on when the Xeons and Pentium 4s implemented it, haven't had a scenario so far that made me want to turn it off.

Me playing around with a P4 HT doing a little 3DMark 2001 + an Ad-Aware scan back in the day. 3rd party app was used to allow two logins to the same computer.

 

[Caring1]

Turned it on when the Xeons and Pentium 4s implemented it, haven't had a scenario so far that made me want to turn it off.

View attachment 107153

Me playing around with a P4 HT doing a little 3DMark 2001 + an Ad-Aware scan back in the day. 3rd party app was used to allow two logins to the same computer.

I had a similar Dell box, it was the GX270 with a P4 in it.
Good little machine to work and play with.

 

[Keullo-e]

I remember my friend running his 2600K with HT off. I said to him that why didn't he get a 2500K then.

In some scenarios HT can lower benchmark scores, but in general, why turn off something which have been the reason to pay more instead of a cheaper model (i7 vs i5)?

 

[Mussels]

I remember my friend running his 2600K with HT off. I said to him that why didn't he get a 2500K then.

In some scenarios HT can lower benchmark scores, but in general, why turn off something which have been the reason to pay more instead of a cheaper model (i7 vs i5)?

2600k had more cache, so it was faster at the same clock speed

 

[Keullo-e]

2600k had more cache, so it was faster at the same clock speed

I know as many i7 does when compared to i5 of the same generation. But i'd not pay that premium just for a little improvement in cache size, and not use HT.