Are there programs that a Turing machine cannot run simultaneously?

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Or, are there parallel running programs that a Turing machine cannot simulate?

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A Turing machine has no problems running (a finite number of) parallel computations. The trick is that it puts the parallel computations after each other on the tape, separated by some delimiter, and then goes through them one by one, one step at the time.

That is, it does the first step in the first computation, records where it is, goes to the second computation, computes the first step, records where it is, goes to the third computation, etc, until it has done the first step in each parallel computation. Then it moves back to where it left the first computation and computes the second step, etc...

If one of the parallel computations runs out of workspace, it pause computation to shift all of the following computations one space up.


So there is no computational power to be gained from parallel computing.