Symmetric doesn't mean 'power of two'. Quite a few ICs have had even numbers of cores on them (I'm not aware of any with an odd number of cores, but that doesn'

Symmetric doesn't mean 'power of two'. Quite a few ICs have had even numbers of cores on them (I'm not aware of any with an odd number of cores, but that doesn't seem like the end of the world either). Lots of other things have to fit on the die, too (e.g. unified cache, which takes up a lot of real estate in chips that have them)