For storage modification machines (pointer machines):
Arnold Schönhage, "Storage Modification Machines" SIAM J. Comput., Vol.9, No. 3, August 1980. Section 5 (Real time simulation of Turing machines) shows how to simulate in real time a 2-dimensional turing machine by a storage modification machine (pointer machine).

Ralf Hinze (email: ralf@informatik.uni-bonn.de)