I'm not trying to be combatitive, but it seems completely arbitrary where one would draw a line and taken to the extreme one is essentially left with a CPU and possibly some RAM that might be some ideal computing machine, but can't even talk to the outside world.
So the whole 'hyperthreading is cool, 2x the CPU' thing: it turns out that as long as your e.g. integer only, true. If you invoke FP, not true: they stall.
L1 cache in some instances is now big enough some people's code never leaves it.
Nobody who lives above a compiler should ever have to worry about this. I live above scripts. I don't really worry about this. I just hark back to when I ran these boxes, on raised floors, remembering how .. distasteful adjunct computing equipment was. It was completely asynchronous, required it's own resets, interfered with cabling, had effects on the bus (unibus!) you didn't entirely understand, they made life "harder" for operations.
Did they speed things up? Sure!
CPU? Ooh you lucky, lucky sod. Back in my day, you wanted an OR gate you had to string some NANDS together.