Man, those people are DENSE. "There is a church". How many chapters ago was that....
@setsu: human brain has exaflop of computational power, and that's a rough estimate. So it likely can process this amount of information, but intuitively/subconsciously.
Regarding the brain storage itself, the hwole thing about him being human tissue could be a lie, and if it isn't, there's Ghost in the SHell "Cyberbrain" which was quite similar.
GITS didn't exactly explain how it works. Only that the brain is encased in a shell, and somehow can be kept alive even when disconnected from the body.