The I7 and I5 processor are quad core processors. The I7 processors include a technology called hyper threading so it is like having twice the amount of cores.
The performance of Intel® Turbo Boost Technology 2.0 and Intel® Hyper-Threading Technology is dynamic, that means that 1 out of the 4 cores from an I7 Processor will be capable to reach the maximum speed when using the Intel® Turbo Boost Technology and your system will do it automatically.
Intel® Hyper-Threading Technology allows each core to perform two tasks simultaneously. This will give a better performance and will complete tasks more quickly.
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No all I5 processors come with hyper threading technology.