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Motorola 68000

Microprocessor / From Wikipedia, the free encyclopedia

The Motorola 68000 (sometimes shortened to Motorola 68k or m68k and usually pronounced "sixty-eight-thousand")[2][3] is a 16/32-bit complex instruction set computer (CISC) microprocessor, introduced in 1979 by Motorola Semiconductor Products Sector.

Quick facts: Designer, Bits, Introduced, Design, Branching...
Motorola 68000 architecture
Introduced1979; 43 years ago (1979)
BranchingCondition code
  • 8× 32-bit data registers
  • 7× 32-bit address registers
  • stack pointer (address register 7)
Quick facts: General information, Launched, Discontinued, ...
Motorola 68000 CPU
General information
DiscontinuedJune 1, 1996; 26 years ago (1996-06-01)
Designed byMotorola
Max. CPU clock rate4 MHz to 16.67 MHz
Data width16 bits
Address width24 bits
Architecture and classification
Instruction setMotorola 68000 series
Physical specifications
  • 64-pin DIP
SuccessorMotorola 68010

The design implements a 32-bit instruction set, with 32-bit registers and a 16-bit internal data bus.[4] The address bus is 24 bits and does not use memory segmentation, which made it easier to program for. Internally, it uses a 16-bit data arithmetic logic unit (ALU) and two more 16-bit ALUs used mostly for addresses,[4] and has a 16-bit external data bus.[5] For this reason, Motorola termed it a 16/32-bit processor.

As 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. It was widely used in a new generation of personal computers with graphical user interfaces, including the Macintosh, Amiga, Atari ST, and X68000. The 1988 Mega Drive console is also powered by a 68000.

The 68000 was followed by additional processors implementing full 32-bit ALUs as part of the growing Motorola 68000 series. The original 68k is generally software forward-compatible with the rest of the line despite being limited to a 16-bit wide external bus.[4]

Pre-release XC68000 chip made in 1979
Die of Motorola 68000

After 43 years in production, the 68000 architecture is still in use.[6][7]