Question on Hyperthreading effects on 2 threaded applications

[scheduleX]

I think this has many answers somewhere but I just want to affirm it in LTT community.

Let's say I have i7 4790K and running a game. Since most of the games are 2 threaded these days, as I can see they only uses up to 25% of the CPU usage in task manager.

From somewhere I read HT cores only has up to 20+% power of physical cores, so if a 2 threaded application uses a physical and a HT cores, will this be slower? Does disabling hyperthreading to ensure they all use physical cores be faster? I am using Windows 7 and GTX 970 btw.

[Atmos]

A Generally in games that use two threads you will see it use threads 1, and 3 on the cpu with hyperthreading. Meaning, practically 0 difference in performance. At least, that's what I've noticed from gaming on my 4790K on arma 3. Instead of using 1, and 2, it uses 1, and 3.

 

And most games these days are moving towards 4 core optimization, not dual core. they require dual cores to even launch much of the time, but run better on up to 4 cores give or take. Only a poorly optimized game will run on two cores in this day and age.

[EMENCII]

@scheduleX

Ok, let's say some things:

1) what do you mean by "most games"? BF uses 4 cores, Far Cry doesn't even start if you dont have 4 cores (and i mean physical...), arma... well, the more you have the better, i have seen improvements even from 4 to 8 cores with that game...

2) seen the point above, i don't know if the percentage of 25 is exact... (GTA5 uses on my pc threads n°3,5,8 at 70%, all the others fluctuating from 30 to 50)...

3) logical cores (HT cores) aren't "real", which means that if you had 5 logical cores on 1 physical, then maybe it would be 20%, but seen that there's 2, i cant see why the first should have 80% of the calculating capability of the entire physical core...

4) you can't use A physical and A logical core, seen that logical cores are... well, not "unusable separately from physical ones"...

5) if you have a 4790k, why would you disable HT? Just buy an i5 4690k ^^

6) no it won't be faster...

 

So, these were my 2 cents, if I'm mistaken somewhere I'm sorry, get me proofs and I'll correct my knowledge on this ^^'

[Nacho Marco Segui]

@scheduleX

Ok, let's say some things:

1) what do you mean by "most games"? BF uses 4 cores, Far Cry doesn't even start if you dont have 4 cores (and i mean physical...), arma... well, the more you have the better, i have seen improvements even from 4 to 8 cores with that game...

2) seen the point above, i don't know if the percentage of 25 is exact... (GTA5 uses on my pc threads n°3,5,8 at 70%, all the others fluctuating from 30 to 50)...

3) logical cores (HT cores) aren't "real", which means that if you had 5 logical cores on 1 physical, then maybe it would be 20%, but seen that there's 2, i cant see why the first should have 80% of the calculating capability of the entire physical core...

4) you can't use A physical and A logical core, seen that logical cores are... well, not "unusable separately from physical ones"...

5) if you have a 4790k, why would you disable HT? Just buy an i5 4690k ^^

6) no it won't be faster...

 

So, these were my 2 cents, if I'm mistaken somewhere I'm sorry, get me proofs and I'll correct my knowledge on this ^^'

Farcry is playable with an i3,no need to patch 

[EMENCII]

Farcry is playable with an i3,no need to patch 

Yeah, well, ok ^^'

But the developers still made it so that it wouldt have started... D:

I know, was really stupid....

[D2ultima]

From somewhere I read HT cores only has up to 20+% power of physical cores, so if a 2 threaded application uses a physical and a HT cores, will this be slower? Does disabling hyperthreading to ensure they all use physical cores be faster? I am using Windows 7 and GTX 970 btw.

Hyperthread cores have potentially +30% benefits, assuming programs use them correctly.

With quadcore + HT CPUs, programs and games will use physical cores before touching hyperthread cores 99% of the time. If you watch your CPU load with a decent program on a game that won't touch hyperthread cores but will touch physical cores, you'll see something like 80% 5% 60% 2% 55% 8% 62% 0% if watching cores #1 through #8 in a row.

Disabling Hyperthreading is naught but a detriment to a 4790K.

Your PC can use hyperthread cores even if games are using physical ones, giving you "free processing power" so to speak. A good example is how an i5 will hit 100% easily in GTA V but an i7 will have excess CPU power (due to the hyperthreads not being fully utilized). It's rare to see any program that isn't a synthetic benchmark pulling a full 100% from a hyperthread-enabled machine. x264 rendering via livestreaming or recording is one (rare) way. Gaming is not.

Here is an explanation I did about more cores and hyperthreads and IPC. It covers more than you asked, but it'll help you to read it anyway.

[scheduleX]

Thanks guys for the replies I have learnt a lot. Just saying, the game I recently playing is Cities Skylines, a city building game, which probably more CPU demanding than any other games out there. Just worrying that it doesn't really utilising my i7 4790k as sometimes I get less than 30 fps.