Is the same speed with more cores/threads better?

[zdemigod]

So I'm a software engineering student and I just heard my teacher say

"If I have a 2 core procesor that is 2ghz speed, it means each core have 1 ghz for itself"

 

Is this true? I thought each core had 2 ghz available for speed.

 

And... Do pc activities consume "cores" or "threads" in multiple threaded applications. But I also heard of "multi core compilation" this uses cores then (counted in pair of threads if the procesor have 8c/16t?)

 

Is there any difference in using cores instead of threads? 

 

Sorry if this is a dumb question and thx for the answers.

[Canada EH]

Just now, zdemigod said:

I just heard my teacher say

Is this a public school, K-12 or a technical college?

[zdemigod]

1 minute ago, Canada EH said:

Is this a public school, K-12 or a technical college?

Is that important? Its a college.

[whoisit1118]

Because if a professor said that, well, he probably doesn't belong in the teaching position. If 2 core processor is 2Ghz, All cores run a 2Ghz. If 16 core threadripper advertises to run at 3Ghz, all cores run at 3Ghz, not 3/16 Ghz.

[Mira Yurizaki]

2 minutes ago, zdemigod said:

So I'm a software engineering student and I just heard my teacher say

"If I have a 2 core procesor that is 2ghz speed, it means each core have 1 ghz for itself"

 

Is this true? I thought each core had 2 ghz available for speed.

No. Each core runs at 2GHz. There's no "pool" of speed that's shared.

2 minutes ago, zdemigod said:

And... Do pc activities consume "cores" or "threads" in multiple threaded applications. But I also heard of "multi core compilation" this uses cores then (counted in pair of threads if the procesor have 8c/16t?)

It depends on what the application is doing and what it wants. An application creates threads to handle some tasks. A web browser for instance spawns threads for handling network traffic, handling the GUI, rendering the HTML, running the JavaScript, and other things. If these threads have things to run, then the OS will put them on cores that are not working on anything at that moment.

2 minutes ago, zdemigod said:

Is there any difference in using cores instead of threads? 

When people talk about "threads" in a processor, what they mean is how many threads from an application that can run on the processor at once. So when you see something like a 4 core/8 thread processor, it means it has 4 physical cores, but the entire processor can handle 8 threads in total (split across 2 threads per core).

 

However the way a core can service two threads at once is that if one thread isn't using all of the execution resources in the core, then the core will see if another thread can use others. So if you have one thread that's doing some simple number crunching with integer numbers, that only takes up some execution resources, leaving the parts that can do floating point with nothing to do. The core then sees if another thread that can use those execution resources is available to run.

 

In short, for the same number of cores, more threads is better. For the same number of threads, more cores is better. So a 4C/8T processor will do better than a 4C/4T processor, but a 8C/8T processor will do better than a 4C/8T processor.

[DJones2894]

These videos should explain multi core cpus and hyper threading.

 

 

 

[Jurrunio]

28 minutes ago, zdemigod said:

If I have a 2 core procesor that is 2ghz speed, it means each core have 1 ghz for itself"

 

More like a 1GHz dual core CPU can do the same amount of work as a 2GHz single core CPU, theoretically.

 

 

[Mira Yurizaki]

2 minutes ago, Jurrunio said:

More like a 1GHz dual core CPU can do the same amount of work as a 2GHz single core CPU, theoretically.

That's true only under the most narrow of circumstances: when everything can be split up evenly and have the same completion time. Otherwise, not accounting for context switching overhead, a single core 2 GHz processor will be higher performing on average than a dual-core 1GHz processor.

 

A case in point, if you have two tasks that take 1 second (@ 1GHz) to complete, both processors will be done at the same time. However, if one of the tasks takes 2 seconds (@ 1GHz) to complete, then the 2GHz processor will be faster ( (1 + 2)/2 = 1.5 seconds).

[whoisit1118]

1 hour ago, M.Yurizaki said:

That's true only under the most narrow of circumstances: when everything can be split up evenly and have the same completion time. Otherwise, not accounting for context switching overhead, a single core 2 GHz processor will be higher performing on average than a dual-core 1GHz processor.

 

A case in point, if you have two tasks that take 1 second (@ 1GHz) to complete, both processors will be done at the same time. However, if one of the tasks takes 2 seconds (@ 1GHz) to complete, then the 2GHz processor will be faster ( (1 + 2)/2 = 1.5 seconds).

That was "theoretically" so I wouldn't be so harsh on it

[pyrojoe34]

1 hour ago, M.Yurizaki said:

That's true only under the most narrow of circumstances: when everything can be split up evenly and have the same completion time. Otherwise, not accounting for context switching overhead, a single core 2 GHz processor will be higher performing on average than a dual-core 1GHz processor.

 

A case in point, if you have two tasks that take 1 second (@ 1GHz) to complete, both processors will be done at the same time. However, if one of the tasks takes 2 seconds (@ 1GHz) to complete, then the 2GHz processor will be faster ( (1 + 2)/2 = 1.5 seconds).

Which is also only true if you are comparing cores of identical design. I can show you a 3.5Ghz quad core that will completely destroy a 5Ghz 8-core in every performance test. Processor performance is so much more complex than a simple reductionist equation using frequency and core/thread count.

[Coaxialgamer]

The speed just refers to the frequency of the central clock circuit. Every core runs at that speed .