I suspect it's very hard if not impossible to work out the actual maximum. Once you add a lot of promoted queens, say, it starts to get difficult to prove the position is legal (i.e. a proof game exists). I think you would have to resort to trial and error and then keep trying to improve the best result.
Position with most possible moves
Sort:
you may well be right, legailty is not so much of a problem if there are no pawns. bajillions is right though...
asimes wrote:
Maybe computational brutality could do it? (Write a program that checks every possible legal position).
I would be kind of surprised if this has not been done. I know that there are a bajillion positions that can be achieved but technically the number is finite. A program left running for a long enough amount of time would find it.
I've seen the numer of total possible chess positions at 10^40.
The mass of the observable universe is around 3*10^52 kg.
yes, a program left running for al ong enough time would find it -- but we'd likely first answer the question of if our universe is going to collapse in on itself or die a cold death first.
A good place to look would be in Tim Krabbe's Chess Curiosities site.
A quick search found me a position (from a real game) where Black had 79 moves at one stage, there may be something else if you are prepared to scratch around.
http://timkr.home.xs4all.nl/records/