MMIX

MMIX (pronounced em-mix) is a 64-bit reduced instruction set computing (RISC) architecture designed by Donald Knuth, with significant contributions by John L. Hennessy (who contributed to the design of the MIPS architecture) and Richard L. Sites (who was an architect of the Alpha architecture). Knuth has said that, MMIX is a computer intended to illustrate machine-level aspects of programming. In my books The Art of Computer Programming, it replaces MIX, the 1960s-style machine that formerly played such a role... I strove to design MMIX so that its machine language would be simple, elegant, and easy to learn. At the same time I was careful to include all of the complexities needed to achieve high performance in practice, so that MMIX could in principle be built and even perhaps be competitive with some of the fastest general-purpose computers in the marketplace." Knuth started the design of MMIX in 1999, and released the stable version of the design in 2011. The processor is numbered as "2009" with Knuth explaining that this is the arithmetic mean from the numbers of other computer architectures; as well as being "MMIX" in Roman numerals. MMIX is a big-endian 64-bit reduced instruction set computer (RISC), with 256 64-bit general-purpose registers, 32 64-bit special-purpose registers, fixed-length 32-bit instructions and a 64-bit virtual address space. The MMIX instruction set comprises 256 opcodes, one of which is reserved for future expansion. MMIX uses IEEE 754 floating-point numbers. All instructions have an associated mnemonic. For example, instruction #20 (32 decimal) is associated with ADD. Most instructions have the symbolic form , where specifies the sort of instruction, X specifies the register used to store the result of the instruction and the rest specify the operands of the instruction. Each of these fields is eight bits wide. For example, means "Set $0 to the sum of$1 and 3." Most instructions can take either immediate values or register contents; thus a single instruction mnemonic may correspond to one of two opcodes.