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:
- Macintosh 128K (7.8336 MHz, January 24, 1984)
- Macintosh 512K (7.8336 MHz, September 10, 1984)
- Macintosh XL (5 MHz, January 1, 1985)
- Macintosh Plus (7.8336 MHz, January 16, 1986)
- Macintosh 512Ke (7.8336 MHz, April 14, 1986)
- Macintosh SE (7.8336 MHz, March 2, 1987)
Quad flat package (QFP) version:
- Macintosh Classic (7.8336 MHz, September 14, 1992)
Variants[]
The 68000 design was revised many times and used in subsequent Macintosh models:
- Motorola 68HC000 - a low power CMOS version, used in the Macintosh Portable and PowerBook 100 at 16MHz each.
- Motorola 68010 - a modestly updated version, which was not used in any Macintosh model.[9]
- Motorola 68020 - a fully 32-bit version with a 3-stage pipeline, used in the Macintosh II and Macintosh LC.
- Motorola 68030 - an update to the the 68020 which incorporated a memory management unit, used in early PowerBooks and the rest of the Macintosh II series, which added built-in support for virtual memory.
- Motorola 68040 - a high-performance version with a 6-stage pipeline, used in the Centris, Quadra, and PowerBook 500 series.
- Motorola 68050 - an update to the 68040 with a planned 64-bit bus and built-in graphics acceleration that was cancelled to redirect resources to the 68060 and a low-power version of the 68040.[10][11]
- Motorola 68060 - a faster superscalar version that was never adopted by Apple Computer as it had instead migrated to PowerPC processors for its Power Macintosh line. A DayStar accelerator had been announced, but was never released.[12]
References[]
- ↑ "Design Philosophy Behind Motorola's MC68000", April 1983. Retrieved on 2018-06-19.
- ↑ "Motorola M68000 Family Programmer's Reference Manual", Motorola, 1992 (archived 2005-10-18), pp. 1-1.
- ↑ Ken Polsson. Chronology of Microprocessors. Processortimeline.info. Retrieved on 2013-09-27.
- ↑ DTACK GROUNDED, The Journal of Simple 68000/16081 Systems (March 1984).
- ↑ 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.
- ↑ Custom 68000 esed on Pre-Production 128k logic boards? by JDW, Applefritter. 2006-11-14.
- ↑ Macintosh Wire Wrap Logic Board #5 1980-1983, Digibarn Computer Museum. 2004.
- ↑ Andy Hertzfeld. Five different Macintoshes. Folklore.org. Retrieved on April 24, 2006.
- ↑ Hacks & Modifications » 68010 in a mac? by uniserver, ThinkClassic. 2014-12-11.
- ↑ Motorola kills the 68050 but the 68060 “could impact PowerPC”, Computer Business Review. 1992-04-14.
- ↑ 68050 by S.A. Fist, The Informatics Handbook: A guide to multimedia communications and broadcasting p.11. 1996.
- ↑ And Daystar 68060 Accelerators... by trag, 68k Macintosh Liberation Army. 2010-02-19.
External links[]
- Motorola 68000 microprocessor family at CPU-World
- 68000 class ICs at CPU-Collection.de
- Motorola 68000 Macs at ForeverMac (archived 2014-08-14, 2011-10-06)
- Chip Hall of Fame: Motorola MC68000 Microprocessor at IEEE Spectrum
- CPUs: Motorola 68000 at Low End Mac (2014-06-14)
- Motorola M68000 Family Programmer’s Reference Manual at NXP (PDF, 1992)
- 68K CPU/FPU pinouts at the Pickle's Low-End Mac FAQ
- M68000 at Sega Retro
- Motorola 68000 at Wikimedia Commons
- Motorola 68000 and Motorola 68000 series at Wikipedia