Too little information to answer your question fully. From what can be gathered from you screen capture, your i5 has 6-cores and you may have set the slider on Full. One of those CPU cores is reserved for the GPU which leaves 5. Examining the log would probably show the CPU core is actually using 4, many projects do not run well on 5 and its multiples on the A7 core.
There is also no information on what else is running on your PC, for instance large numbers of interrupts would slow down CPU processing.
Posting your log file would be better for figuring out what is going on - viewtopic.php?p=327412&f=24#p327412