It isn't actually two hardware threads, and the one core never does two things at once. I don't think that's quite true. Rather, the two "virtual cores" are m

It isn't actually two hardware threads, and the one core never does two things at once. I don't think that's quite true. Rather, the two "virtual cores" are mostly independent, but share some backend resources. For example, modern Intel CPU's can sustain execution of 4 instructions per cycle, and with hyperthreading, two of these instructions can be from one thread and two from the other. Or one and three, or four and zero. Both threads truly do execute at the same time, it's just that the competition for resources means it sometimes takes longer for them to execute on a shared core than on separate physical cores.