 Weak Turing machines are machines where some word over the alphabet is repeated infinitely often to the left and right of the input. Semi-weak machines are machines where some word is repeated infinitely often either to the left or right of the input. These machines are generalizations of the standard model in which the initial tape contains some finite word (possibly nil). They were introduced to determine smaller universal machines. Watanabe was the first to define a universal semi-weak machine with six states and five symbols (Watanabe 1961). Recently, a number of researchers have determined several small weak and semi-weak universal Turing machines (e.g., Woods &amp; Neary 2007; Cook 2004)