The MOS 6502 Microprocessor
The Motorola/MOS 6502 microprocessor could be considered the most impactful invention for computing since the initial creation of the transistor. This is due to many different reasons, but the first and most important of those is money. In 1974, home computing had not been developed, with computer systems and large-scale mainframes only being used by government and individual businesses for accountancy purposes, or specific scientific operations.[i]
The Motorola 6800 microprocessor could be considered its direct predecessor regarding how it handles not only the key issue of power supply, but also the needed usage of a clock oscillator on the chip itself. This would simplify not only the needed peripherals for the chipset, and overall computer, but more importantly the overall design of the main motherboard.[ii] This advancement in how the chip would be controlled would lead to further refinements of operating system creation and software coding. While the 6502, on paper, is far less powerful than either the IBM 8080 or the 6800, its stripped-back features allowed it to be produced at a greatly reduced cost.[iii]
“The MOS Technology 650X family represents a conscious attempt of eight former Motorola employees who worked on the development of the 6800 system to put out a part that would replace and outperform the 6800, yet undersell it. With the benefit of hindsight gained on the 6800 project, the MOS Technology team headed by Chuck Peddle, made the following architectural changes in the Motorola CPU…”
On average, microprocessor production would be relatively cheap for the mid 1970s, usually on average $75.00 for a ceramic coated chip, and $5.00-$10.00 for a standard plastic-coated chip.[iv] This allowed MOS, and later Motorola to sell the 6502 at a rock-bottom price of $25 dollars in 1975. This extreme price drop from the standard rate of $175-$360 for a microprocessor created a price war situation between the major producers of computer products at this point in time. IBM, Commodore, Motorola, MOS, and even Texas Instruments would engage in price gouging to try to ensure that their own products would be bought over the others’ products. This in turn would lead up to the rapid development of personal-sized computers, including the original Apple I microcomputer, the Commodore PET, the Apple II, the BBC Micro, the Commodore VIC-20, and various Atari 8-bit computers.[v]
The importance of the creation of many of these devices would start the Home Computer Revolution starting in 1977. This is the beginning of what would become the computer world that would develop in the 1990s, and the 21st century.[vi] The development of the Commodore PET and the original drafting of the BASIC coding language would also lead to the development of the first Microsoft and Macintosh software products, including the important development of DOS, as a coding language and operating system.
With these developments taking place over the space of about 3 years, it is apparent that the development of the 6502 microprocessor was instrumental in the rapid modernization of the home computer market, and the overall technology of minimizing the machines, and allowing them to become more accessible to the average consumer, instead of just the business or laboratory integrations. With these implementations, the scope of coding and computing requirements shifted from the likes of FORTRAN operating code, and assembly-based language required by higher-level scientific applications.
The development of BASIC as a programming language and eventual operating system baseline would be partially worked through the specific limitations of the 6502 microprocessor. Unlike the more capable and feature rich 6800 or 8080 that were released around the same time as it, the 6502 would streamline and simplify the instruction sets that would be utilized by the computer itself. One of the more important ideas that were introduced within the 6502 was the process of allowing certain address spaces to be referenced directly by whatever program is being referenced in the code.
In conclusion, regarding the importance of the 6502 microprocessor, the functionality of it would be inspirational regarding future processor production, with its origins being visible even today in the Windows operating system, with certain assembly commands still redirecting towards the original BASIC commands that were developed at the start of Microsoft’s company. The further iterations of the processor, including the 6503, 6504, 6505, 6507, 6508, 6509, and 6510.[vii] Following the development of the original 6502, however, the newer versions of the chip were developed with a variety of different applications, and thus had different specific engineering goals. The 6502 and 6501 both had 40 pins, and the following models were reduced to 28 pins, and while that would reduce capabilities, it expanded the applications for the chip.[viii]
[i] Ho, Joshua (9 October 2014). "An Introduction to Semiconductor Physics, Technology, and Industry". Anandtech. Archived from the original on 24 February 2020. Retrieved June 21st, 2024.
[ii] US3987418A, Buchanan, John K., "Chip topography for MOS integrated circuitry microprocessor chip", issued 1976-10-19 Archived 2024-06-21 at the Wayback Machine
[iii] "Motorola mounts M6800 drive". Electronics. 48 (8). New York: McGraw-Hill: 25. April 17, 1975. "Distributors are being stocked with the M6800 family, and the division is also offering an introductory kit that includes the family's six initial parts, plus applications and programming manuals, for $300."
[iv] "MOS 6502 the second of a low cost high performance microprocessor family". Computer. 8 (9). IEEE Computer Society: 38–39. September 1975. doi:10.1109/C-M.1975.219074. Archived from the original on 2021-02-24. Retrieved 2024-06-21.
[v] Reimer, Jeremy. "Personal Computer Market Share: 1975-2004". Archived from the original on 6 June 2012. Retrieved 2024-06-21.
[vi] Ibid.
[vii]Draco (19 June 1997). "65c02, 6502, 65816 ??? CPU sells but who's buying..." Archived from the original on 2 January 2008, accessed June 21st, 2024.
[viii] Lawrence P. Forsley. "Embedded systems: 1990 Rochester Forth Conference: June 12 – 16th, 1990 University of Rochester" Archived 2015-03-25 at the Wayback Machine. p. 51.