All physical computers are equivalent to finite state machines, due to the fact that their memory is not infinite.

A computer with 64 megs of RAM along with 8 32-bit registers has a total of 536871168 bits of memory. Hence, such a machine can take on a finite number of states, namely: 2^536871168 states.

It's a collossal number of states, but the fact is, all computers with finite memory are finite state machines.