Oct 08 2018

Total recall: “6502: igniting the digital revolution” (2017)

The 6502 was pure magic out of transistors. The creators of this microchip are truly digital heroes that achieved the unthinkable: creating a low-cost microprocessor in 1975 that shaped the electronic industry. This device was used in legendary machines, such as Atari VCS 2600, Apple II, Commodore 64, Nintendo Famicon, etc. An animated GIF is worth one thousand words:

(sometimes this GIF does not animate, try this)

In 2017 I gave two talks on this topic. First, in April 2017, I had the opportunity to pay homage to this wonderful tiny microprocessor by means of a presentation at the retrocomputing event RetroMadrid. Later, I extended a little bit the talk and gave it again as part of a research divulgation event organized by the government of Madrid (Semana de la Ciencia 2017, November 2017).  I deeply enjoyed the process of connecting the numerous dots that outline a fascinating and unique story. Also, I received lots of feedback from the audience that I very much appreciate. By the way, the end of the second talk is alternative… in many senses.

The contents of the talk cover:

  • Brief (and quite informal) review on digital circuits and integrated circuits
  • Chuck Peddle and Motorola: let’s compete with Intel!
  • Chuck Peddle and MOS Technology: Let’s build a low-cost microprocessor!
    • The 650x team
    • Design of the 650x chipset
    • Selling the micro
    • Motorola strikes back
  • 6502 and Commodore
  • 6502 and… Commodores, Atari, Apple, ARM, Nintendo, etc., etc.
  • The 6502 today
    • Books, microchips and kits
    • FPGAs
    • Visual6502
    • 6502 and neuroscience
  • The public goes wild


I must highlight that my talks were based on books and documents that later on I realized that some of them were not completely objective, so the story had some uncertainties that must be further investigated. I wish I have the time some day to do so. Since then, I try to be very careful with the sources I used and I always try to elaborate my own version of the story, clearly stating what is fact and what is an opinion (mine of somebody else’s). [I talked a little bit about that in my talk about the invention of the microprocessor]

Summarizing, no matter if you are sentimentally attached to Zilog, Motorola, Texas Instruments, etc., the story of the 6502 must be told, because this microprocessor is a key element to understand the creation of the PC and the birth of the videogame industry.

Some highlights

  • The microelectronic process was manual. They had to draw the different layers of the microchip by hand. This also happens with the Intel 4004.
  • A guy called Steve Wozniak bought a few chips from the first batch of 6502 to build the Apple I. This microprocessor made possible to build affordable computers.
  • Two of the three first best-seller personal computers that motivated IBM to enter the personal computer business had 6502 as brains: Apple II (6502), Commodore PET (6502) and Tandy TRS-80 (Z80).
  • The creation of the 6502 and the fact that a small company (Western Design Center) could design and produce microchip served as an inspiration to Acorn engineers to develop their own microprocessors and a few years later ARM was born.



6502.org: The 6502 microprocessor resource
The Visual 6502 project: Wanna see the transistor activity while executing assembly code? This is the place
Apple][ history website: The reference place to learn about the Apple ][
Commodore: a company on the edge: Amazing book about the first steps of Commodore Bussiness Machines into computing. The inception of the 6502 chip is beautifully described.

Talks (in Spanish)

  • El microprocesador 6502 y su impacto en la revolución digital (Spanish),  RetroMadrid 2017, [slides]
  • Historia del microprocesador 6502: semilla del PC y de la industria de los videojuegos (Spanish), Semana de la Ciencia 2017 [slides (with alternative ending 🙂 )]

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