Less cores with higher clock speed or more cores with less clock speed?

[DazzlingWhisker]

Hi,

 

I wonder if my understanding is right:

 

If you have a 2 cores at 4 GHz or 4 cores at 2 GHz (NONE OF THEM IS HYPER THREADED) the performance is based on if the application (game for example) can handle 4 cores or not. If it can only handle 2 cores, then the it would be better to have a 2 core CPU at 4 GHz than if you have a 4 core CPU at 2 GHz.  Is that right?

 

But how is it if you have a 2 core CPUat 4 GHz and a 4 core CPU at 2GHz if the application (game for example) can handle 4 cores. What's better than? 2 cores at 4 GHz and 4 cores at 2GHz. Should they perform the same?

 

I watched a video about this but didn't really understand.

 

[3 Lions]

The CPU with the more physical cores would be better.

[DazzlingWhisker]

1 minute ago, LinusTechTipsFanFromDarlo said:

The CPU with the more physical cores would be better.

Why?

[3 Lions]

Just now, DazzlingWhisker said:

Why?

Because the workflow can be split up between the extra 2 physical cores on the die resulting in better processing. 

[Theguywhobea]

3 minutes ago, DazzlingWhisker said:

Hi,

 

I wonder if my understanding is right:

 

If you have a 2 cores at 4 GHz or 4 cores at 2 GHz, the performance is based on if the application (game for example) can handle 4 cores or not. If it can only handle 2 cores, then the it would be better to have a 2 core CPU at 4 GHz than if you have a 4 core CPU at 2 GHz.  Is that right?

 

But how is it if you have a 2 core CPUat 4 GHz and a 4 core CPU at 2GHz if the application (game for example) can handle 4 cores. What's better than? 2 cores at 4 GHz and 4 cores at 2GHz. Should they perform the same?

 

I watched a video about this but didn't really understand.

I guess it would also depend if this 4 physical cores or 4 logical cores? A 2C/2T CPU at 4GHz would still be better than a 2C/4T CPU at 2GHz. But in general yes, if a program can use more cores, it will run better with a more cores versus a faster clock speed with less cores.

[Sack]

Think of it like car lanes, and in this case, the 2 core represents two lanes where no one else can drive on those lanes until those cars are at their destination. The 4 core can serve 4 cars at a time albeit, at a slower speed, this means that the 4 core can handle more stuff at the same time without having to ask for more cars, while the 2 core is faster it also has to ask  for new cars all the time, in addition, not all process will max out the speed of your CPU for different reasons.

[Bananasplit_00]

depends on how the program is parelalised and how well it scales with extra cores

[DazzlingWhisker]

2 minutes ago, Sack said:

Think of it like car lanes, and in this case, the 2 core represents two lanes where no one else can drive on those lanes until those cars are at their destination. The 4 core can serve 4 cars at a time albeit, at a slower speed, this means that the 4 core can handle more stuff at the same time without having to ask for more cars, while the 2 core is faster it also has to ask  for new cars all the time, in addition, not all process will max out the speed of your CPU for different reasons.

Good explenation, thx. But if 2 cars can drive in a faster speed than 4 cars at a lower speed, if the 2 cars are driving double the speed of the 4 other cars, won't the 2 cars and the 4 cars come to the destination att the same time?

[Sack]

Just now, DazzlingWhisker said:

Good explenation, thx. But if 2 cars can drive in a faster speed than 4 cars at a lower speed, if the 2 cars are driving double the speed of the 4 other cars, won't the 2 cars and the 4 cars come to the destination att the same time?

The point is that the 2 cars don't always drive at 2x speed, maybe they only need to drive 200 m and then they turn off that highway, and then the highway will let 2 new cars onto its road. If they did drive at full speed your CPU would see 100% utilization, which it should almost never do.

[heimdali]

This is far more complicated than you think.  Scaling to multiple cores involves overhead, scheduling tasks across more cores also involves overhead, accessing RAM involves latency, and when you have multiple nodes, NUMA comes into the picture.

 

If your machine delivers the performance you desire also depends on a lot more factors than only clock speed.  To get the best performance, you need to tailor the system for the specific workload.

 

[heimdali]

2 minutes ago, Sack said:

The point is that the 2 cars don't always drive at 2x speed, maybe they only need to drive 200 m and then they turn off that highway, and then the highway will let 2 new cars onto its road. If they did drive at full speed your CPU would see 100% utilization, which it should almost never do.

There´s nothing wrong with 100% CPU load --- in a way, it´s the most efficient thing.

 

The problem is more like that the 2 fast cars have accidents while the 4 cars can get stuck in traffic jam.

 

[SquintyG33Rs]

13 minutes ago, DazzlingWhisker said:

Hi,

 

I wonder if my understanding is right:

 

If you have a 2 cores at 4 GHz or 4 cores at 2 GHz (NONE OF THEM IS HYPER THREADED) the performance is based on if the application (game for example) can handle 4 cores or not. If it can only handle 2 cores, then the it would be better to have a 2 core CPU at 4 GHz than if you have a 4 core CPU at 2 GHz.  Is that right?

 

But how is it if you have a 2 core CPUat 4 GHz and a 4 core CPU at 2GHz if the application (game for example) can handle 4 cores. What's better than? 2 cores at 4 GHz and 4 cores at 2GHz. Should they perform the same?

 

I watched a video about this but didn't really understand.

 

since most things don't use multiple threads you would be better suited to get the 2 core CPU for general use. it will complete the tasks faster and jump on to the next one faster.

also 2GHz is almost a crippling slow speed at this point, i know it's just a hypothetical question though. the real complete answer for gaming depends on if you want to play AAA games or mostly "other" because only those titles use the extra power. for example PUBG on my G3258@4.5 is much better than on my Ryzen 1700@3.9 and it's true for MMORPG games or league(not that this one matters) or pretty much anything that isn't Ubisoft EA activision console port...

[KenjiUmino]

20 minutes ago, DazzlingWhisker said:

If you have a 2 cores at 4 GHz or 4 cores at 2 GHz

can i haz 3 cores at 3 GHz

[heimdali]

2 minutes ago, KenjiUmino said:

can i haz 3 cores at 3 GHz

You can have 2x6x2@3.06 plus turbo.  I think you can have 3 only when one is broken.

 

[heimdali]

8 minutes ago, SquintyG33Rs said:

since most things don't use multiple threads you would be better suited to get the 2 core CPU for general use. it will complete the tasks faster and jump on to the next one faster.

also 2GHz is almost a crippling slow speed at this point, i know it's just a hypothetical question though. the real complete answer for gaming depends on if you want to play AAA games or mostly "other" because only those titles use the extra power. for example PUBG on my G3258@4.5 is much better than on my Ryzen 1700@3.9 and it's true for MMORPG games or league(not that this one matters) or pretty much anything that isn't Ubisoft EA activision console port...

Is this PUBG so badly optimized or what´s the problem?

 

2GHz isn´t crippling at all, depending on what you´re doing.

 

[Dylanc1500]

It entirely depends on if all the instructions being performed are something that is parallel or serial logic. Most applications have a mix of instructions some of which can be more serial or parallel in nature. It's a logic issue as not all tasks can be parallelized so in those instances the faster you can perform each function the better. However some logic is highly parallel and each task can be processed concurrently in which case throwing more cores can be more optimal. It's not always a matter of optimization as some tasks can only be broken down so far before clock speed starts to take effect.

[ARikozuM]

Getting more work done is always better... READ: Both are equally important.

 

You're reliant on core count only to the point where the engine calls for physical cores (hyperthreading is handled by the OS, not the engine) and logical cores will complement them for scheduling purposes (seldom do they undertake calculations). Once you reach the number of cores the engine can utilize, you need to focus on frequency so that those cores can do more within a second or clock cycle. It's why the 1500X, 1600, and 1800X have the same gaming score as engines largely utilize four cores (plus their SMT which is allocated by the OS) as they aren't able to fully saturate the pipeline. 

 

Ryzen is in a weird spot with its inter-CCX latency where a multi-threaded function needs to talk across a larger gap versus a monolithic die like Intel's consumer and enthusiast platforms (mesh/X299 notwithstanding).

 

One thing to consider is that all games using multiple cores are largely single-threaded and sequential, i.e. multiple core usage does not equate to multi-threaded functions. You can multi-thread certain things that aren't crucial like weather or AI (though most in-game AI is stupid as f#ck) in certain games, but combat has to be single-threaded as a stop or wait in the function could cause issues with the outcome of an action. 

[Coldphil2]

For gaming I would suggest the 2 physical cores at 4GHz, because as Linus has said many times games are difficult to parallelize.  This has to do with how games are reliant on user input rather than a specific line of code that the computer knows how to execute ahead of time. More cores will not help you if they don't have anything to do. If all the work is being done by core #1 or #2 then #3 & #4 are there twiddling their virtual thumbs.

But if you are looking for productivity, like image editing and rendering, the more core less GHz CPU will benefit you more. Hence the whole line of Xeon and Extreme Edition i7 CPUs aimed at servers and content creators.

[Crunchy Dragon]

17 minutes ago, Coldphil2 said:

For gaming I would suggest the 2 physical cores at 4GHz, because as Linus has said many times games are difficult to parallelize.  This has to do with how games are reliant on user input rather than a specific line of code that the computer knows how to execute ahead of time. More cores will not help you if they don't have anything to do. If all the work is being done by core #1 or #2 then #3 & #4 are there twiddling their virtual thumbs.

But if you are looking for productivity, like image editing and rendering, the more core less GHz CPU will benefit you more. Hence the whole line of Xeon and Extreme Edition i7 CPUs aimed at servers and content creators.

I agree with this, 2 physical cores is the absolute minimum for even light gaming. The AMD A6-5400K I have in my desktop isn't a true dual-core CPU, it's a 1 core/2 thread CPU and struggles to do even basic tasks. Dual core gaming is starting to go out of style

 

Gaming is generally a single-threaded application, which means that games currently can't take as much advantage of higher core/thread counts. This is why Intel CPUs are still the king of gaming PCs.

 

It's worth mentioning, @Coldphil2, that the Extreme Edition lineup are aimed at enthusiasts and content creators like streamers and youtubers moreso than general consumers. Personally, I wouldn't get anything less than 4 physical cores for a gaming rig, for example one of the Coffee Lake Core i3s or a Core i5.

 

 

[geo3]

3 hours ago, LinusTechTipsFanFromDarlo said:

The CPU with the more physical cores would be better.

Wrong. Not all work loads can be divided. In fact many can't. Half the cores at double the Ghz will always be faster. Under even the most ideal conditions for parallel processing the higher core slower clock will only ever match the performance. 

 

The only reason multi core cpu's started existing is because it's becoming harder and harder to push IPC and frequency beyond what they already are.

 

Given a market of an 8Ghz 1 core, 4Ghz 2 core and 2 Ghz 4 core cpus, assuming the same architecture and caches sizes, I will always go for the single core.

[SquintyG33Rs]

3 hours ago, heimdali said:

Is this PUBG so badly optimized or what´s the problem?

 

2GHz isn´t crippling at all, depending on what you´re doing.

 

well it kinda is you'll see network speed and transfer speeds (copying files or moving them between drives) slow down at that kind of CPU speed now with the faster devices and networks we use. but yeah for everyday usage it's not very noticeable at all.

 

i wouldn't say it's badly optimized. that's more what ubisoft does.... here it's a design flaw  when they started working on the engine. Unreal is very capable engine but clearly the devs here didn't really know what they were doing. and it's a very common problem with indie teams.

[DazzlingWhisker]

On 2017-11-07 at 8:11 PM, Dylanc1500 said:

It entirely depends on if all the instructions being performed are something that is parallel or serial logic. Most applications have a mix of instructions some of which can be more serial or parallel in nature. It's a logic issue as not all tasks can be parallelized so in those instances the faster you can perform each function the better. However some logic is highly parallel and each task can be processed concurrently in which case throwing more cores can be more optimal. It's not always a matter of optimization as some tasks can only be broken down so far before clock speed starts to take effect.

Thx for the answer. 

 

But if you have 2 cores @ 4GHz or 4 cores @ 2GHz AND if the program CAN handle multiple cores, which of them would be faster then? It does it really matter if 2 stuff is happening at the same time but at half the speed or if first the first instruction happens and then the other at double the speed?

[DazzlingWhisker]

23 hours ago, Coldphil2 said:

For gaming I would suggest the 2 physical cores at 4GHz, because as Linus has said many times games are difficult to parallelize.  This has to do with how games are reliant on user input rather than a specific line of code that the computer knows how to execute ahead of time. More cores will not help you if they don't have anything to do. If all the work is being done by core #1 or #2 then #3 & #4 are there twiddling their virtual thumbs.

But if you are looking for productivity, like image editing and rendering, the more core less GHz CPU will benefit you more. Hence the whole line of Xeon and Extreme Edition i7 CPUs aimed at servers and content creators.

Thx.

 

You say that it's better to have 4 cores @ 2GHz rather tham 2 cores @ 4 GHz in video editing and rendering. I know that those things utalizes more cores, but why will it be faster to spread the work over 4 cores @ 2 GHz rather than 2 cores @ 4Ghz? 2 cores @ 4Ghz can already handle a lot of things at the same time, so WHY is it better with 4 cores then?

[Coldphil2]

30 minutes ago, DazzlingWhisker said:

Thx.

 

You say that it's better to have 4 cores @ 2GHz rather tham 2 cores @ 4 GHz in video editing and rendering. I know that those things utalizes more cores, but why will it be faster to spread the work over 4 cores @ 2 GHz rather than 2 cores @ 4Ghz? 2 cores @ 4Ghz can already handle a lot of things at the same time, so WHY is it better with 4 cores then?

I don't have the perfect answer for why a lower clock speed is more beneficial because logic would tell you 4 cores and 4Ghz would be the best of both worlds. But what I do know is that when you have something like rendering and editing, being able to spread those workloads around to more cores is always better. Linus uses the painfully simple example of a single core CPU trying to multiply 2x3x4. If it has only one core it would look like this:

Core 1:

2x3=6

6x4=24

Where as a dual core could do it like this:

Core 1:

2x3=6

While Core 2 does:

4x6=24

Effectively doing things twice as fast, now that is not saying 2 cores is twice as fast a single core or anything. But how that you can cut down on workload times by having more cores.

It isn't a perfect example but it does help to illustrate how in heavily threaded applications, you can almost always use more cores.

 

 

 

[PianoPlayer88Key]

On this thread, and in many other discussions on core/thread count, I very rarely see discussion on running multiple tasks simultaneously.  It almost always seems to center on running a single program or game, with minimal background processes running.  This definitely does NOT reflect how I use a computing device.

 

In multitasking situations, would there be a little overhead with trying to run / schedule multiple apps on the same core, vs running them on separate cores?

 

What do you guys think would be better for someone whose workload is like the screenshots below?

 

  

 

  

 

  

 

  

 

 

I'm thinking, for a multitasker like me, a CPU with more cores, as well as more RAM, would be better than fewer cores, generally.  (If I could afford it, I might have a dual or quad socket Xeon or Epyc system.)