That was me, a very long time ago.
The computer simulation would take less than seconds, and would be run on servers either at the beginning of the game or just prior. We just view it in "real time". It would probably work backwards, working out which team wins the match-up, by how much... and work out how the game gets there post that.
To think that the game actually occurs on servers as it's played out on our screens is a little naive.
http://with-malice.com/ - The half-crazed ramblings of a Lakers fanatic in Japan