The Zilog Z800 was a 16-bit microprocessor designed by Zilog and meant to be released in 1985. It was instruction compatible with their existing Z80, and differed primarily in having on-chip cache and a memory management unit (MMU) to provide a 16 MB address range. It also added a huge number of new more orthogonal instructions and addressing modes. The Z800 contrasts with Zilog's first 16-bit effort, the Zilog Z8000, in that the Z800 was intended to be Z80 compatible, while the Z8000 was only Z80-like and did not offer any direct compatibility.