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Motorola MC68000L8 MACSS processor

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[]

Motorola MC68HC000FN12F QFP processor

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:

Motorola XC68040RC25M processor

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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