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MOS MCS6502 microprocessor

A MCS6502 processor, a rare early variant that had been used in the Apple I computer

The MOS Technology 6502, often simply referred to as 6502, was a low-cost 8-bit processor that was produced by MOS Technology, and later Commodore International. It became widely used in early computers, such as the Apple I, Commodore PET and VIC-20, as well as early game systems, such as the Atari 5200.


Electrical engineer Chuck Peddle had worked on the Motorola 6800 processor in 1973, which was priced at US$300 per unit in a kit. Motorola turned down his proposal to produce a simplified processor to meet marketplace demand for a lower-cost processor. Peddle and some other Motorola engineers then left for MOS Technology, where they formed a small team to design the MOS 6501 and 6502, which became available in 1975 at a fraction of the cost of the Motorola 6800 and Intel 8080.[1][2]

In November 1975, Motorola filed a lawsuit against MOS Technology for patent infringement and misappropriation of trade secrets.[3] MOS settled the case in March 1976 for $200,000 and cancelling the 6501 processor, which was socket-compatible with the 6800.[4] In November 1976, MOS was acquired by Commodore International, which produced the 6502 and variants for its own computer line.[5]

Steve Wozniak obtained early units of the 6502 from Chuck Peddle for use in the Apple I computer. After Commodore acquired MOS, Apple obtained subsequent processors from Synertek for their Apple II and III series.[6]


The 6502 design was revised many times and licensed to different manufacturers:

Video tutorials[]


  1. Phil Lemmons (1982-11). BYTE Interview: Chuck Peddle pp. 256-270. BYTE Magazine.
  2. Chuck Peddle. Centre for Computing History. Retrieved on 2017-07-10.
  3. Waller, Larry. "News briefs: Motorola seeks to stop microprocessor foe", McGraw-Hill, November 13, 1975, p. 38. "Motorola said last week it would seek an immediate injunction to stop MOS Technology Inc., Norristown, Pa., from making and selling microprocessor products, including its MCS6500." (This issue was published on November 7.)
  4. "Motorola, MOS Technology settle patent suit", McGraw-Hill, April 1, 1975, p. 39.  "MOS Technology Inc. of Norristown, Pa. has agreed to withdraw its MCS6501 microprocessor from the market and to pay Motorola Inc. $200000 ..." "MOS Technology and eight former Motorola employees have given back, under court order documents that Motorola contends are confidential." "…both companies have agreed to a cross license relating to patents in the microprocessor field."
  5. "Mergers and Acquisitions", Cahners, November 1976, p. 19. " Commodore International … is buying MOS Technology (Norristown, PA). This saves the six-year-old semiconductor house from impending disaster."
  6. Correct 6502 for an Apple II Rev 0? by MarkO, Apple Fritter. 2016-01-28.

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