Something about the I series that's confusing?

Ok, can someone answer me this please?... I know its probably simple but I still have a hard time finding decent info...

Say you have an I7-720qm. It turbo's to 2.8 single core, 2.4 dual core, 1.7 3 or more.

So, does single core mean 1 physical core plus 1 hyperthread? or does this mean only 1 physical core? likewise does the 2.4 dual core mean 1 physical plus 1 hyperthread or 2 physical cores plus 2 hyper threads?

Thanks for being patient with me. I look this mess up and they want you to read through numerous pages of Intel performance articles and so on.

Best Wishes,

StevenX

 

I believe it would be:

1 cores 2 thread @ 2.8GHz
2 cores 4 threads @ 2.4GHz
3-4 cores 6-8 threads @ 1.7GHz

 

Hyperthreading gives each core 2 identical threads instead of 1. There is no "real core" and no "fake core." Each physical core will always have the two threads, unless of course you shut off hyperthreading.

The thing is though, you will do a single core turbo boost if you are only using one thread. If you use two threads it will split this between two cores. Hyperthreading improves the efficiency of a single core when running multiple high intensity threads by 0-30%, but running another core as well is going to increase performance by nearly 100%. When what you are running is able to take advantage of multiple threads, going to more slower cores is a lot better than going to less faster cores.

 

Yes, Trottel has it correct (sorry 'j0KER).

Only one thread, it will clock to 2.8GHz Maximum.

As soon as you have two threads, it will clock to 2.4GHz Maximum.

When your application(s) hit three threads, it will clock to 1.7GHz Maximum.


Why the 'Maximum', above? Because this depends on the ambient temps, the internal temps in the notebook and the cooling design (how efficient it is in removing the built-up heat) of the notebook - in addition to the specific processor in use (production variance).

Because of all the above, even if it can initially hit the higher frequencies, doesn't mean it can sustain them (with the same, identical workload).

 

Wait wut? So how/when will hyperthreading kick in? What decides whether it uses a core or a second thread of a core?

 

AFAIK, all physical cores are used first, then the 'hyper-threading' cores are used. This assumes perfectly written/executed software though, of course.

 

The OS knows which two virtual cores correspond to each core of the processor. It will try to load one virtual core of each core before loading two virtual cores of the the same core. There is no sense in overloading a single core with more work when there is another sitting idle.

 

Thanks so much everyone. This makes sense.
1. Physical threads/cores used first
2. 1 = single core boost, 2 = dual core boost, 3+ = lowest boost.
3. Temp and Demand factor into boost.

This makes sense now. Again I appreciate everyone's help!

StevenX

 

Hey! I got one right?

Glad to have been of some help.