An early Motorola "MACSS" 68000, like the one used in the Macintosh 128K.

The Motorola 68000, also referred to as the 68000 or 68k, is a 16/32-bit CISC processor that was produced by Motorola's Semiconductor Products Sector. The 68000 was used in the Apple Lisa and early models of Amiga, Atari ST, and Macintosh computers.

History

Development on the 68000 began in 1976 as the Motorola Advanced Computer System on Silicon (MACSS) project to create a new design to replace the Motorola 6800, which had been surpassed by competitors such as the MOS 6502. It contained a 32-bit instruction set which ran at high speeds for the era, a 24-bit address bus which could address up to 16 MB of RAM,[1] and 16-bit external data bus.[2]

The original 68000 was announced in September 1979 and was fabricated using a HMOS process with a 3.5 µm feature size.[3] Initial samples were released in February 1980, with production chips becoming publicly available in November.[4]

The performance improvements of the 68000 over previous microprocessors led to a 5MHz version being used in the Apple Lisa to help drive its graphical user interface.[5] In January 1983, Motorola provided custom batches, marked "SC87839L", to Apple's Macintosh development team. These units have appeared in early Macintosh prototypes.[6][7] An 8 Mhz version (clocked to 7.8336 MHz) would be used in the original Macintosh 128K.[8]

Mac models with 68000 processors

Dual in-line package (DIP) version:

Quad flat package (QFP) version:

Variants

A Motorola 68HC000 like the one used in the Macintosh Portable and PowerBook 100.

The 68000 design was revised many times and used in subsequent Macintosh models:

The Motorola 68040 was used in the Macintosh Quadra line.

References

  1. "Design Philosophy Behind Motorola's MC68000", April 1983. Retrieved on 2018-06-19. 
  2. "Motorola M68000 Family Programmer's Reference Manual", Motorola, 1992 (archived 2005-10-18), pp. 1-1. 
  3. Ken Polsson. Chronology of Microprocessors. Processortimeline.info. Retrieved on 2013-09-27.
  4. DTACK GROUNDED, The Journal of Simple 68000/16081 Systems (March 1984).
  5. Simon, Jeffrey S. Young, William L.. "iCon : Steve Jobs, the greatest second act in the history of business", Wiley (retrieved via Google Books), 2006-04-14. Retrieved on 2014-01-06. 
  6. Custom 68000 esed on Pre-Production 128k logic boards? by JDW, Applefritter. 2006-11-14.
  7. Macintosh Wire Wrap Logic Board #5 1980-1983, Digibarn Computer Museum. 2004.
  8. Andy Hertzfeld. Five different Macintoshes. Folklore.org. Retrieved on April 24, 2006.
  9. Hacks & Modifications » 68010 in a mac? by uniserver, ThinkClassic. 2014-12-11.
  10. Motorola kills the 68050 but the 68060 “could impact PowerPC”, Computer Business Review. 1992-04-14.
  11. 68050 by S.A. Fist, The Informatics Handbook: A guide to multimedia communications and broadcasting p.11. 1996.
  12. And Daystar 68060 Accelerators... by trag, 68k Macintosh Liberation Army. 2010-02-19.

External links

Motorola 68k series processors
Central processing units : 68000 · 68010 · 68020 · 68030 · 68040 · 68050 · 68060
Floating-point units :   (n/a)  ·   (n/a)  · 68881 · 68882 · (SANE)
Memory management units :   (n/a)  · 68451 · 68851
Other :                           (VI475)
Superseded by PowerPC processors in March 1994
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