The Motorola 680x0/m68k/68k/68K is a family of 32-bit CISC microprocessors. During the 1980s and early 1990s, they were popular in personal computers and workstations and were the primary competitors of Intel's x86 microprocessors. Although no modern desktop computers are based on the 68k, derivative processors are still widely used in embedded applications. As of 1998, the 68K family was the best-selling 32-bit architecture in the world. 79 million 68K chips were sold in 1997, compared to about 75 million Pentium-based PCs.[1]
Family members
- Generation one (internally 16/32-bit, and produced with 8-, 16-, and 32-bit interfaces)
- Motorola 68000
- Motorola 68EC000
- Motorola 68HC000
- Motorola 68008
- Motorola 68010
- Motorola 68012
- Generation two (fully 32-bit)
- Motorola 68020
- Motorola 68EC020
- Motorola 68030
- Motorola 68EC030
- Generation three (pipelined)
- Motorola 68040
- Motorola 68EC040
- Motorola 68LC040
- Generation four (superscalar)
- Motorola 68060
- Motorola 68EC060
- Motorola 68LC060
- Others
- Freescale 683XX (CPU32 aka 68330, 68360 aka QUICC)
- Freescale ColdFire
- Freescale DragonBall
Improvement roadmap
The 68020 improved this:
- 32-bit address & ALU.
- 3 stage pipeline.
- Instruction cache of 256 bytes.
- Unrestricted word and longword data access (see alignment).
- 8 x multiprocessing capability.
- Larger multiply (32×32 -> 64 bits) and divide (64÷32 -> 32 bits quotient and 32 bits remainder) instructions, and bit field manipulations.
- Addressing modes added scaled indexing and another level of indirection.
- Low cost, EC = 24-bit address.
68030:
- Split instruction and data cache of 256 bytes each
- On-chip MMU (68851).
- Low cost EC = No MMU.
68040:
- Instruction and data caches of 4 kilobytes each
- 6 stage pipeline.
- FPU lacks IEEE transcendental functions capability.
- FPU emulation works with 2E71M and later chip revisions.
- Low cost LC = No FPU.
- Low cost EC = No FPU & MMU.
68060:
- Integer pipeline.
- Two cycle integer multiplication unit.
- Branch prediction.
- Dual instruction pipeline.
- Instructions in the address generation unit (AGU) and thereby supply the result two cycles before the ALU.
- Low cost LC = No MMU.
- Low cost EC = No MMU & FPU.
Main uses
The 68k line of processors has been used in a variety of systems, from modern high-end Texas Instruments calculators (the TI-89, TI-92, andVoyage 200 lines) to all of the members of the Palm Pilot series that run Palm OS 1.x to 4.x (OS 5.x is ARM-based), and even radiation hardened versions in the critical control systems of the Space Shuttle. However, they became most well-known as the processors poweringdesktop computers such as the Apple Macintosh, the Sinclair QL, the Commodore Amiga, the Atari ST, and several others. The 68k was also the processor of choice in the 1980s for Unix workstations and servers from firms such as Sun Microsystems, NeXT and Silicon Graphics. There was a 68k version of CP/M.
Today, these systems are either end-of-line (in the case of the Atari), or are using different processors (in the case of Amiga, Macintosh, Sun, and SGI). Since these platforms are now more than two decades old, their original manufacturers are unlikely to support an operating system for this hardware or are even out of business. However, the Linux, NetBSD and OpenBSD operating systems still include support for 68k processors.
The 68k processors were also used in the Sega Mega Drive/Sega Genesis and SNK Neo Geo consoles as the main CPU. Other consoles such as the Sega Saturn used the 68k for audio processing and other I/O tasks, while the Atari Jaguar included a 68000 which was intended for basic system control and input processing, but due to the Jaguar's unusual assortment of heterogeneous processors was also frequently used for running game logic.
Microcontrollers derived from the 68k family have been used in a huge variety of applications. For example, CPU32 and ColdFire microcontrollers have been manufactured in the millions as automotive engine controllers.
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