I'm pretty sure the answer there is "no". I've heard of a couple of methods that are almost purely computational: Measure the randomness of something like rad

I'm pretty sure the answer there is "no". I've heard of a couple of methods that are almost purely computational: Measure the randomness of something like radioactive decay, try to figure out the PRNG used in the simulation. Measure all those very basic constants of the universe to a large number of decimal points. See if they indicate register size of the simulator.