Why is not dualcore twice as fast as singlecore

imperator's Avatar

imperator

29 Mar, 2018 06:20 PM

Hello I want to put a simply question. Why is dualcore score not same as 2x singlecore score.

For example iphone 7
singlecore 3400 | multicore 5700

There is around 20% lower score for all multicore points.
So you can simply explain why ? Is it common access to RAM ? Or one core wait for second core or what ? Thanks

  1. Support Staff 1 Posted by Colin on 29 Mar, 2018 10:16 PM

    Colin's Avatar

    Hi,

    Thanks for reaching out to us about this. A device's multi-core score is not expected to be a simple multiple of its single-core score, in general. One of the major contributing factors to this is that many devices have different types of cores, with some being more powerful and some being more energy-efficient (or having other benefits). In the case of the iPhone 7 and its A10 Fusion processor, it has two high-performance cores and two high-efficiency cores, all of which are tested by the multi-core benchmark. The multi-core benchmark does involve some communication between cores and access to memory which could also affect the end result, though factors which limit performance can differ between devices.

    Could you expand a bit on what you mean by "around 20% lower score for all multicore points. "? Do you mean that 3400x2 would be 6800, which is about 20% higher than 5700?

    All the best,
    Colin
    Primate Labs Inc.

  2. 2 Posted by imperator on 30 Mar, 2018 01:25 PM

    imperator's Avatar

    Hi thanks for your reply.

    Yes I mean that for example iphone 6s
    2200 x 2 = 4400
    but multicore is 3800 - it is about 16% less.

    So both cores can't be 100% utilized - or can be utilized for 100% but there is other bottleneck - e.g. access to ram can't be simultaneously for both cores in the same time etc... But it is only my opinion - i want from you - technical explanation.

    Or in desktop cpu are more degradation in quad or octa core cpu - most time amd
    intel utilize quad core very well

    can degradation depends on performance controller or some unit which put instruction on cores ?

    Thanks.

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