Motorola 68000

Historia

The Motorola 68000 (sixty-eight-thousand; also called the m68k or Motorola 68k, sixty-eight-kay) is a 16/32-bit CISC microprocessor, introduced in 1979 by Motorola Semiconductor Products Sector. The first member of Motorolas family of 16- and 32-bit processors. Successor to the 6809 and followed by the 68010. The 68000 has 32-bit registers but only a 16-bit ALU and external data bus. It has 24-bit addressing and a linear address space. Addresses are computed as 32 bit, but the top 8 bits are cut to fit the address bus into a 64-pin package (address and data share a bus in the 40 pin packages of the 8086). The 68000 has sixteen 32-bit registers, split into data and address registers. Like many other CPUs of its generation, it can fetch the next instruction during execution (2 stage pipeline). The 68000 was used in many workstations, notably early Sun-2 machines, and home computers like Apple Macintosh, Commodore Amiga and Atari ST series. Variants of the 68000 include the 68HC000 (a low-power HCMOS implementation) and the 68008 (an eight-bit data bus version used in the Sinclair QL). The 68EC000 is a 68000 with selectable 8 or 16 bit data bus and A0.