That is a cool paper (and there is an unpaywalled PDF [1]), but what that it shows is not that the Z3 is Turing complete, but that a larger machine comprising a

That is a cool paper (and there is an unpaywalled PDF [1]), but what that it shows is not that the Z3 is Turing complete, but that a larger machine comprising a Z3 and a piece of sticky tape is Turing complete. The Z3 as built and used was not Turing complete. Moreover, the technique in the paper is purely a stunt. You couldn't do practical branching computation that way. It is definitely cool, but it doesn't change the fact that the Z3 was a calculator, not a computer. [1] http://www.inf.fu-berlin.de/inst/ag-ki/rojas_home/documents/1997/Universal_Computer.pdf http://www.inf.fu-berlin.de/inst/ag-ki/rojas_home/documents/...