cores vs threads

[pmarion427]

hi,

 

just wondering what are the differences between a 2 core cpu and a 1 core cpu with 2 threads, or 4 cores vs 2 w/ hyperthreading, etc.

 

i think threads are like virtual cores but does that influence perfomance?

[mapegl]

Well 2 threads just means the core will still only work one task at a time, but basically switches back and forth, therefore simulating 2 cores and using the left over performance of that particular core. 2 Threads on a single core is always better than just one thread on one  core, but 2 cores with a single thread each will always beat 2 threads on a single core. Hope that makes sense.....

 

I would always choose a quad-core without hyperthreading over a dual-core w/ hyperthreading, but a quad-core with hyperthreading might be faster than one without. Although I could not name anything besides rendering and such where you might need that.

[JR1911]

2 physical cores is better than one core with hyperthreading.

[FireFox]

Basically Hyper-Threading is a queueing technology which queues two threads which the core and process when required. I can't remember if it is actual hardware built into the die itself or just on a software level, I can't remember.

 

Anyway I think it is something like that, without spending the next hour reading about it again then I'm not 100% sure that is correct so take it with a pinch of salt.

 

If I am wrong though please point it out to me.

 

Hypertheading helps with performance but day to day you'll not notice anything, when it comes to multi-threaded applications is where you'll notice it.

[vm'N]

A thread is essentially a line of code. A core a "little" CPU.

 

A core can process multiple threads at once, this is called SMT.

 

Intel have implemented SMT into their design, this is what Intel calls Hyper-threading.

 

Hyper-threading doesn't switch back and forth between the threads, which is an untrue rumour.

 

Hyper-threading allows another thread to be process simultaneously. These two threads are sharing the resources, and non are giving an constant priority over the other, which is another untrue rumour.

[vm'N]

Basically Hyper-Threading is a queueing technology which queues two threads which the core and process when required. I can't remember if it is actual hardware built into the die itself or just on a software level, I can't remember.

 

Anyway I think it is something like that, without spending the next hour reading about it again then I'm not 100% sure that is correct so take it with a pinch of salt.

 

If I am wrong though please point it out to me.

 

Hypertheading helps with performance but day to day you'll not notice anything, when it comes to multi-threaded applications is where you'll notice it.

They only change the fetch, and might the memory pipeline slightly.

[FireFox]

They only change the fetch, and might the memory pipeline slightly.

 

Am I completely wrong then or partially wrong?

[vm'N]

Am I completely wrong then or partially wrong?

Hyperthreading is "hardly" a physical implementation unlike FX modules which are almost entirely physical implementations. The fact that HT is not entirely a physical implementation is where I think people get the misconception of "virtual cores" and "logical cores" and all that crap.

 

So you are not off tracks.

[FireFox]

Hyperthreading is "hardly" a physical implementation unlike FX modules which are almost entirely physical implementations. The fact that HT is not entirely a physical implementation is where I think people get the misconception of "virtual cores" and "logical cores" and all that crap.

 

So you are not of tracks.

 

So I am on the right track or off the right track?

[vm'N]

You are ON track. Edited my last post, saw the part which brought up this confusion-

[FellTheSky]

2 physical cores is better than one core with hyperthreading.

thats way too simplistic. 1 haswell core will count for 2 amd. But if its from intel to intel, yes 2 cores is better than 1c/1t (i3vsi5)

[FireFox]

You are ON track. Edited my last post, saw the part which brought up this confusion-

 

Ahh no worries

[JR1911]

thats way too simplistic. 1 haswell core will count for 2 amd. But if its from intel to intel, yes 2 cores is better than 1c/1t (i3vsi5)

 

Yes, that's what I meant, I should have elaborated that if the only difference between the cores is HT then two cores will always be better than one. However if the cores are completely different then it can't be simplified like I did.

 

[Faa]

Hyperthreading is "hardly" a physical implementation unlike FX modules which are almost entirely physical implementations. The fact that HT is not entirely a physical implementation is where I think people get the misconception of "virtual cores" and "logical cores" and all that crap.

 

So you are not off tracks.

Hyperthreading is a physical implementation: Hyper-threading works by duplicating certain sections of the processor—those that store the architectural state—but not duplicating the main execution resources. http://en.wikipedia.org/wiki/Architectural_state

The whole point behind HT is pulling more out of your core, performance varies between a little to twice as much performance. A single core with HT could perform exactly the same as two cores without HT.

[vm'N]

Well, I never said SMT wasn't an physical implementation.

 

SMT is in use because newer architecture have such an wide execution pipeline that it is hard for software to utilize it all.