Intel Multi threading question

[Spezcrt]

Is it good to enable hyper threading if having a low resolution monitor (ex: 1366x768), does enable HT decrease performance on these low resolution monitor ?

[Bananasplit_00]

why would it? its pure performance gain unless you are pushing a single core to the absolute max overclock you can pretty much

[Spezcrt]

I don't overclock, should I enable HT on low resolution monitor or not ?

[mariushm]

Hyperthreading doesn't have anything to do with resolution, it simply creates additional cpu cores that a game may or may not use.

At lower resolutions, games will finish computations faster so you'll get more fps and the video card driver may use more cpu to push more fps to the monitor (if the monitor can do more than 60fps)

However, if the game engine was not designed to use more than 2-4 cores to do those computations, then it makes no difference if you have HT or not enabled as the game will still be stuck with 2-4 cores.

 

What's your reasoning to assume some effect HT would have on lower resolutions?

 

 

[demonkoi]

there is no reason to disable multi threading unless you are doing a very specialized workload

[Spezcrt]

Since not very much game today depend on HT so enable it on would make some games decrease fps, if we have a cpu i7 3770 and a gpu rx 580 on a 1366x768 monitor then we must have to enable Vsync to lock the fps to 60 so the gpu not have to work hard and waste go to heat, is turn on Vsync and HT make a good combination ?

[mariushm]

You're making some strange assumptions.

Enabling HT doesn't reduce the performance of existing cores, so why would games decrease fps when HT is enabled?

 

Each core has some resources available, multiplication units, addition units, various things... not all are used at the same time when computations are made by a thread running on a core. So a fake core created by hyperthreading "borrows" those units that are not used by other cores at a specific time to perform calculations on them.

The original cores still run at the same frequency, at the same performance, they're not affected... the original cores never used those units in the first place so they don't care.

 

If you have a 4 core processor and the game only uses 2 cores and you enable hyperthreading to get 8 cores (4 real and 4 fake cores), the game will STILL use only 2 cores, and most likely the operating system will put the threads of that game on two real cores. If the OS puts them on a hyperthreading core, then it's not a problem, the HT core always has free "units" to borrow from the other four cores, so you don't lose performance.

 

Where you can get slight performance drops is for example if the game is really well made and can take advantage by lots of cores, like let's say up to 8 cores. So if you have the game running with 4 cores, the game will adjust itself to run with 4 threads or whatever it thinks it best to use the 4 cores to the maximum.

When you enable hyperthreading to get 8 cores, such game may readjust itself to use 8 threads and in some cases, and all eight threads may do some heavy computations ... but since the original 4 cores have most of their "units" busy, the four hyperthreading cores often can't borrow units from the other cores to do computations, so these hyper cores would end up slower than the real cores.

So the game may lose a bit of performance if it constantly has to wait for the threads on hypercores to finish their jobs, which eventually happens when the threads on the original cores finish their jobs so the units of those cores become available and can be borrowed by the hyper cores.

 

So it only has effect if the game is really CPU bound, like strategy games, maybe games like Civilization, turn based strategy games with AI and crap like that..

When you reduce the resolution so low, you're basically reducing the amount the video card has to work, so video card finishes each frame fast, so you're pushing the game to compute more, but again.. if the game isn't designed to use loads of cores and load them to maximum, it won't be affected by hyperthreading.

[Mira Yurizaki]

33 minutes ago, NikcSpoi said:

Since not very much game today depend on HT so enable it on would make some games decrease fps, if we have a cpu i7 3770 and a gpu rx 580 on a 1366x768 monitor then we must have to enable Vsync to lock the fps to 60 so the gpu not have to work hard and waste go to heat, is turn on Vsync and HT make a good combination ?

I suggest leaving HyperThreading enabled unless you can find strong evidence that whatever you're doing has a negative performance impact on the games you play. HyperThreading normally doesn't impact performance in either direction to make much of a difference even with the configuration you're thinking of.

 

The only way I can think of that enabling HyperThreading would reduce performance is if threads from another application were already on a core and there's not enough execution resources for the game's thread to run. But if that was the case, I wouldn't think disabling HyperThreading would help either.

[Spezcrt]

Alright guys, i am going with HT enable, thanks for explaining !