Mechanical Turing machines can be small, such as: https://hackaday.com/2018/03/08/mechanical-wooden-turing-machine/ https://hackaday.com/2018/03/08/mechanical-w

Mechanical Turing machines can be small, such as: https://hackaday.com/2018/03/08/mechanical-wooden-turing-machine/ https://hackaday.com/2018/03/08/mechanical-wooden-turing-mac... They will take a long time to compute something like SHA2