From Donald E. Knuth's MMIX page: MMIX is a RISC computer designed by the author to illustrate machine-level aspects of programming. In the next editions of his books The Art of Computer Programming, MMIX will replace the 1960s-style machine MIX. More details can be found in his book: MMIXware: A RISC Computer for the Third Millennium, by Donald E. Knuth (Heidelberg: Springer-Verlag, 1999), viii+550pp. ISBN 3-540-66938-8. (Lecture Notes in Computer Science, no. 1750.) Some MIX programs have been converted to MMIX, and can be found at http://www.mmixmasters.org/~mmixmasters/