MOS 6502

The MOS Technology 6502, often simply referred to as 6502, was a low-cost 8-bit processor that was produced by , and later . It became widely used in early computers, such as the Apple I, and , as well as early game systems, such as the .
==History==
Electrical engineer had worked on the processor in 1973, which was priced at 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 .
In November 1975, Motorola filed a lawsuit against MOS Technology for patent infringement and misappropriation of trade secrets."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.) MOS settled the case in March 1976 for $200,000 and cancelling the 6501 processor, which was socket-compatible with the 6800. "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." In November 1976, MOS was acquired by Commodore International, which produced the 6502 and variants for its own computer line." Commodore International … is buying MOS Technology (Norristown, PA). This saves the six-year-old semiconductor house from impending disaster."
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 for their Apple II and III series.Correct 6502 for an Apple II Rev 0? by MarkO, Apple Fritter. 2016-01-28.
==Variants==
The 6502 design was revised many times and licensed to different manufacturers:
*MOS MCS6502 - a rare early version of the MOS 6502 which was used in the Apple I computer.
* SY6502 - a d version used in Apple II computers after MOS was acquired by Commodore.
*Synertek SY6502A/B - a faster version used in Apple III computers.
*MOS 6502B/C - even faster versions used in the , , , and .
*NCR/GTE - a low-power CMOS version used in the Apple IIc and Apple IIe.
* - an ultra low-cost version used in the .
* - an enhanced version used in the .
*WDC 65C816 - a backwards-compatible 16-bit version used in the Apple IIGS.
==Video tutorials==
“Hello, world” from scratch on a 6502 — Part 1
How do CPUs read machine code? — 6502 part 2
Assembly language vs. machine code — 6502 part 3
==References==
==External links==
*6502.org the 6502 microprocessor resource
*650x class ICs at CPU-Collection.de
*MOS Technology 6502 microprocessor family at CPU-World
*Chip Hall of Fame: MOS Technology 6502 Microprocessor at IEEE Spectrum
*Processors at Apple Logic
* at Wikipedia
===Articles===
*The Rise of MOS Technology & The 6502 by Ian Matthews at Commodore.ca (2003-02-15, 2006-01-18)
*How The Dis-integrated 6502 Came To Be by Mike Szczys at Hackaday (2016-05-24)
*The Good Old 6502 Microprocessor, But 7000x Bigger! by Farhad Modaresi at The Journal of Science and Technology (2020-10-15)
Category:Microprocessors
Category:1975 introductions