The MACSS aimed to develop an entirely new architecture without backward compatibility with the 6800. This became the Motorola Advanced Computer System on Silicon project, or MACSS, begun in 1976. As the sales prospects of the 6800 dimmed, Motorola began a new design to replace it.
Although a capable design, it was eclipsed by more powerful designs, such as the Zilog Z80, and less expensive designs, such as the MOS Technology 6502 (MOS 6502). Motorola's first widely-produced CPU was the Motorola 6800. Motorola MC68000 ( plastic leaded chip carrier (PLCC) package) The original 68k is generally software forward-compatible with the rest of the line despite being limited to a 16-bit wide external bus. The 68k was soon expanded with more family members, implementing full 32-bit ALUs as part of the growing Motorola 68000 series. The 1988 Mega Drive console is also powered by a 68000.
It was widely used in a new generation of personal computers with graphical user interfaces, including the Macintosh, Amiga, Atari ST, and X68000. For this reason, Motorola termed it a 16/32-bit processor.Īs one of the first widely available processors with a 32-bit instruction set, and running at relatively high speeds for the era, the 68k was a popular design through the 1980s. Internally, it uses a 16-bit data arithmetic logic unit (ALU) and two more 16-bit ALUs used mostly for addresses, and has a 16-bit external data bus. The address bus is 24 bits and does not use memory segmentation, which made it easier to program for. The design implements a 32-bit instruction set, with 32-bit registers and a 16-bit internal data bus. The Motorola 68000 (sometimes shortened to Motorola 68k or m68k and usually pronounced "sixty-eight-thousand") is a 16/32-bit complex instruction set computer (CISC) microprocessor, introduced in 1979 by Motorola Semiconductor Products Sector.
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