Although it is also a very good point that even with modern hardware many orders of magnitude faster than the emulated hardware, most emulators have to resort to timing hacks to make everything run smoothly, and because of timing inconsistencies when locking, parallelism is of limited use even when emulating multiple hardware components that originally ran in parallel. To emulate a human brain, we're probably either going to need far more sensitive locking across multiple cores than is currently even imagined, or we're going to have to emulate the whole massively parallel thing on a single thread on a CPU much, much more powerful than a brain.