Multi core CPUs

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Aria abbasi

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Hello,

Nowadays most of the PCs have a multi-core CPU with a clock speed in GHZ. My question is about that clock speed and the cores.
For example consider a CPU which has a 2 actual cores and 2 virtual cores (e.g., Intel core i3) and the computer system properties shows the 3.0 GHz as clock cycle speed.

1- Does that (say) 3.0 GHz show the clock speed of each core (from that core i3 CPU so that totally speed will be 4*3.0 GHZ = 12.0 GHZ!?) or that 3.0 GHZ is the entire speed of all cores?

2- Do the virtual cores have the identical effect as the actual cores in performance!?

And as well as I have a question about ROM :).
Do ROMs anymore exist in current new PCes?

Thanks.
 
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Eximo
Pretty well covered in everyone's responses, not sure what there is to add.

I guess your unnumbered question: Yes computers still use ROM in the form of EEPROM BIOS chips. It is called Read Only Memory only in name though, this stores the 'firmware' and settings of your BIOS, as long as power is applied, the Read Only part remains when power is shut off, the firmware/BIOS itself.

1) Yes and No, each physical and logical core runs at that frequency, but in no way is it totaled.
2) No, and it varies on the program that is running. Many applications are still single threaded and will use a single processing core, others are multi-threaded but poorly optimized and do not see much benefit from hyperthreading.
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Eximo

Eximo

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1) GHz and Hz are just literal measurements of frequency. They don't really relate to performance except when comparing the exact same architecture of chips (Such as comparing a 10 year old Pentium 4 3.0Ghz, to a modern day Pentium labeled chip)

2) Hyperthreading allows the processor to run additional tasks simultaneously. In practice I believe a 'virtual' core outputs adds between 25% and 50% actual performance compared to having another physical core.
 
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FabioZ

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Hi,
The different cores/virtual cores give the processor the ability to do things in parallel. That is, more things at the same time. On the other hand, the clock speed would be the speed of each core by itself.
There are tasks that can be done faster when parallelized, and other's that can't.
Imagine this: Each cores add another lane to the road, and the clock speed determines the speed at which the cars travel on each lane.
On virtual vs real cores, real ones tend to perform better than virtual ones (that's one of the reasons why core i5s are more powerful than i3s).
Hope this helped!
 
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Eximo

Eximo

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Pretty well covered in everyone's responses, not sure what there is to add.

I guess your unnumbered question: Yes computers still use ROM in the form of EEPROM BIOS chips. It is called Read Only Memory only in name though, this stores the 'firmware' and settings of your BIOS, as long as power is applied, the Read Only part remains when power is shut off, the firmware/BIOS itself.

1) Yes and No, each physical and logical core runs at that frequency, but in no way is it totaled.
2) No, and it varies on the program that is running. Many applications are still single threaded and will use a single processing core, others are multi-threaded but poorly optimized and do not see much benefit from hyperthreading.
 
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Aria abbasi

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thank you very much. About the firmware and EEPROM. Is the EEPROM a box that contains the firmware which that firmware in turn contains the BIOS settings?
And is it correct that, a logical core in fact uses the actual/physical core for its computing but when that physical core is idle?
 
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Eximo

Eximo

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Not sure what you mean on the first one. EEPROM is a type of memory that the BIOS is stored on.

I don't think any of that information on logical cores is accurate. Not really a good way to describe it in simple terms, but it is sort of like a single physical core running two virtual cores so that the OS perceives two cores. They share the same core, resources, and information. It is more dynamic then just running when there is idle time on the core. It allows for actual simultaneous threading.
 
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