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Multi core CPUs

By abbasi
Oct 13, 2014
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  1. 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 [​IMG] .
    Do ROMs anymore exist in current new PCes?

    Thanks.
     
    Last edited: Oct 13, 2014
  2. GhostRyder

    GhostRyder This guy again... Posts: 2,191   +590

    Well yes each "Core" including virtual's (Normally the hyperthreaded ones famous on Intel CPU's now) will show up with the same clock speed base as the real cores. Windows specifically views a processor that contains 2 cores and 4 threads (IE an i3 on desktop for instance) as a quad core processor in the processor hardware area.

    Do the virtual cores have the same effects as a physical core in performance? No, the virtual cores are not as good as a real core. So for instance having the same processor spec to spec wise with 4 cores versus one with 2 cores and 4 threads the 4 cores would win out in overall performance. Hyper threaded or virtual cores do help but they are not as good as the real deal.
     
    abbasi likes this.
  3. abbasi

    abbasi TS Booster Topic Starter Posts: 307   +21

    Thanks. What about questions no. one and three? :)
     
  4. GhostRyder

    GhostRyder This guy again... Posts: 2,191   +590

    Which was the third question?

    As for the first sorry I forgot to answer that, you do not add up the "ghz" of all the processor cores to get the speed. But it is that every "Physical" core runs at the 3.0ghz clock speed so essentially you could say that the i3 is running at 6.0ghz because the two physical cores are running at 3.0ghz but generally you would not add them up. You normally also do not take Virtual cores into account because they generally do not work the same way a normal core does. They essentially run 2 processes on the same processor core so essentially they are sharing the workload when possible.

    For exactly what's going on this link can help explain in great detail.
     
    abbasi likes this.
  5. abbasi

    abbasi TS Booster Topic Starter Posts: 307   +21

    My system information says this about the processor:
    Intel core i3 2120 CPU 3.3 GHZ 2 cores 4 logical processors.
    What does that mean please? Does my have 3.3 Ghz or 6.6 Ghz totally?

    My third question was about ROMs :)
     
  6. JohnCB

    JohnCB TS Booster Posts: 118   +62

    Lets do this through an anology, we'll use cars.

    You have a Toyota Corolla that can do 90mph with 4 logical engines. That doesn't mean the car can go 360mph, it just means it can always go 90mph because if you keep adding more people and weight tot he car, the extra engines pick up the slack to ensure you are always going the maximum possible speed.

    This isn't the most accurate analogy, but should hopefully help explain the idea behind dual-cores, virtual processors, hyperthreading, etc.
     
    abbasi likes this.
  7. GhostRyder

    GhostRyder This guy again... Posts: 2,191   +590

    Well if you think of it that way there would be 6.6ghz total because there are two Physical cores each running at 3.3ghz on your machine. But normally you do not add up the amount as a total when comparing.

    As for the ROM's question yes.
     
    abbasi likes this.
  8. abbasi

    abbasi TS Booster Topic Starter Posts: 307   +21

    So the maximum speed is 3.3 Ghz but with more cores we can be ensured that most of the time that maximum speed is utilized and more apps are running, yes?
     
  9. JohnCB

    JohnCB TS Booster Posts: 118   +62

    In the most simplistic of terms, yes that's a good basic understanding.

    However, keep in mind, software needs to be written to take advantage of multiple cores to get the full potential out of it.
     
    abbasi likes this.
  10. cliffordcooley

    cliffordcooley TS Guardian Fighter Posts: 8,550   +2,894

    Lets see if I can make any sense with my thoughts, whether true or not. Please bare in mind, I'm referencing Intel not AMD.

    It is my understanding that the frequency is the max physical speed at which each core can operate. And because of single-thread core inefficiency, Hyper-threading was introduced. Hyper-threading will time slice the frequency to maximize the single-core efficiency rating with two threads running at once. So in essence Hyper-threaded CPU's will run both threads within that core frequency. Simply put Hyper-threading is not multiples of frequency, but efficiency gains instead.
     
    abbasi likes this.
  11. abbasi

    abbasi TS Booster Topic Starter Posts: 307   +21

    Thanks to all.
    And as an another question :)
    Suppose I have 4 cores X 1.6 GHz CPU. That is 4 cores each core has 1.6 GHz speed. And another CPU with 2 cores X 2.3 GHz. That is 2 cores each core has 2.3 GHz speed.
    The first one has more cores but the second one has more speed per each core. Which one has better performance?
     
    Last edited: Oct 14, 2014
  12. cliffordcooley

    cliffordcooley TS Guardian Fighter Posts: 8,550   +2,894

    Think of it this way, each generation increases on the amount of work that can be done per clock cycle of the CPU. So unless we theorize about the amount of work per clock cycle being equal for both CPU's, there is no way to answer your question. With a single core working at a specific frequency, you get a specific amount of work done. With 4 cores at the same frequency theoretically you get 4 times the amount of work done.

    Assuming work per clock cycle is equal for both CPU's single core.
    4x1.6 [6.4] > 2x2.3 [4.6]

    Keep in mind though the frequency is not being multiplied, we are adding multiple channels of the same frequency together to get a very rough output generalization.
     
    abbasi likes this.
  13. abbasi

    abbasi TS Booster Topic Starter Posts: 307   +21

    OK. Great explanation. So more than one basic computation can be done per clock cycle! I wouldn't know this!
    Let I get more info from you :). The more core and more logical cores are all benefit just for parallel computing? That is only when the parallel computing can be utilized those more physical/logical cores are useful, yes?
     
  14. cliffordcooley

    cliffordcooley TS Guardian Fighter Posts: 8,550   +2,894

    Think of clock cycles as the number of steps it takes you to complete a mathematic equation on paper. The CPU has to take steps and the clock ticks is what moves it from step to step at the designated frequency.
    I don't know the processes of computing, just the most basic functionality.
     
    abbasi likes this.
  15. abbasi

    abbasi TS Booster Topic Starter Posts: 307   +21

    OK. Thanks for all of your responses of you.
     
  16. GhostRyder

    GhostRyder This guy again... Posts: 2,191   +590

    Yes but it all also depends on the software being used. Many times things are coded more for a max of 2 - 4 cores meaning that even if you say had 6 Physical cores that say if the program was only programmed to use 2 cores then the other 4 would almost be wasted.

    Having more cores can be beneficial especially if comparing using a quad core to a dual core. However sometimes having fewer stronger cores can be better than having a bunch of weak cores.
     
    abbasi likes this.
  17. abbasi

    abbasi TS Booster Topic Starter Posts: 307   +21

    Excellent clarifying!
    Thank you very much.
     

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