Motorola began making transistors in 1950 and had a portfolio of semiconductor patents.
He had since moved on and was doing some very interesting work on calculator chipsets at a new company he formed in Valley Forge, Pennsylvania. Paivinen had formed MOS Technology in 1969 with two other executives from General Instrument, Mort Jaffe and Don McLaughlin.
Allen-Bradley, a supplier of electronic components and industrial controls, acquired a majority interest in 1970.
Motorola started the 6800 microprocessor project in 1971 with Tom Bennett as the main architect.
Bill Mensch joined Motorola in June 1971 after graduating from the University of Arizona (at age 26).
The chip layout began in late 1972, the first 6800 chips were fabricated in February 1974 and the full family was officially released in November 1974.
In May 1972, Motorola's engineers began visiting select customers and sharing the details of their proposed 8-bit microprocessor system with ROM, RAM, parallel and serial interfaces.
Bennett hired Chuck Peddle in 1973 to do architectural support work on the 6800 family products already in progress.
The price of the working examples had to cover the production cost of the 90% that were thrown away. In 1973, Perkin-Elmer introduced the Micralign system, which projected an image of the mask on the wafer instead of requiring direct contact.
The chip layout began in late 1972, the first 6800 chips were fabricated in February 1974 and the full family was officially released in November 1974.
In early 1974, they provided engineering samples of the chips so that customers could prototype their designs.
On 19 August 1974, Chuck Peddle, Bill Mensch, Rod Orgill, Harry Bawcom, Ray Hirt, Terry Holdt, and Wil Mathys left Motorola to join MOS.
On October 30, 1974, Motorola had filed numerous patent applications on the microprocessor family and was granted twenty-five patents.
The design team had formerly worked at Motorola on the Motorola 6800 project; the 6502 is essentially a simplified, less expensive and faster version of that design. When it was introduced in 1975, the 6502 was the least expensive microprocessor on the market by a considerable margin.
In a November 1975 interview, Motorola's Chairman, Robert Galvin, ultimately agreed that Peddle's concept was a good one and that the division missed an opportunity, "We did not choose the right leaders in the Semiconductor Products division." The division was reorganized and the management replaced.
He delivered on the promise, the new line was ready by June 1975. ===Design notes=== Chuck Peddle, Rod Orgill, and Wil Mathys designed the initial architecture of the new processors.
A September 1975 article in EDN magazine gives this summary of the design: 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.
Chuck Peddle's goal was to sell the first run 6501 and 6502 chips to the attendees at the Wescon trade show in San Francisco beginning on September 16, 1975.
One of the earliest was a full-page story on the MCS6501 and MCS6502 microprocessors in the July 24, 1975 issue of Electronics magazine.
Stories also ran in EE Times (August 24, 1975), EDN (September 20, 1975), Electronic News (November 3, 1975), Byte (November 1975) and Microcomputer Digest (November 1975).
Advertisements for the 6501 appeared in several publications the first week of August 1975.
In September 1975, the advertisements included both the 6501 and the 6502 microprocessors.
In October 1975, Motorola reduced the price of a single 6800 microprocessor from $175 to $69.
On November 3, 1975, Motorola sought an injunction in Federal Court to stop MOS Technology from making and selling microprocessor products.
The next revision of the layout fixed this problem and the May 1976 datasheet listed 56 instructions.
The first was in June 1976 and the second was to Bill Mensch on July 6, 1976, for the 6820 PIA chip layout.
In March 1976, the now independent MOS Technology was running out of money and had to settle the case.
Another roughly similar product was the Synertek SYM-1. One of the first "public" uses for the design was the Apple I microcomputer, introduced in 1976.
MOS left the instruction out of chip documentation entirely because of the defect, promising that ROR would appear on 6502 chips starting in 1976.
Transcript ==Further reading== Datasheets and manuals 6500 Series Datasheet; MOS Technology; 12 pages; 1976. 6500 Series Hardware Manual; 2nd Ed; MOS Technology; 182 pages; 1976. 6500 Series Programming Manual; 2nd Ed; MOS Technology; 262 pages; 1976. Books 6502 Applications Book; 1st Ed; Rodnay Zaks; Sybex; 281 pages; 1979; .
The 6502 was next used in the Commodore PET and the Apple II, both released in 1977.
Transcript ==Further reading== Datasheets and manuals 6500 Series Datasheet; MOS Technology; 12 pages; 1976. 6500 Series Hardware Manual; 2nd Ed; MOS Technology; 182 pages; 1976. 6500 Series Programming Manual; 2nd Ed; MOS Technology; 262 pages; 1976. Books 6502 Applications Book; 1st Ed; Rodnay Zaks; Sybex; 281 pages; 1979; .
Along with the Zilog Z80, it sparked a series of projects that resulted in the [computer] revolution of the early 1980s. Popular video game consoles and computers, such as the Atari 2600, Atari 8-bit family, Apple II, Nintendo Entertainment System, Commodore 64, Atari Lynx, BBC Micro and others, use the 6502 or variations of the basic design.
The Atari Lynx used a 4 MHz version of the chip, the 65SC02. In the 1980s, a popular electronics magazine Elektor/Elektuur used the processor in its microprocessor development board Junior Computer. ==Technical description== The 6502 is a little-endian 8-bit processor with a 16-bit address bus.
When faster memories became available in the 1980s, newer machines could run at higher clock rates, like the 2 MHz CPU in the BBC Micro, and still use the bus sharing techniques. ===Registers=== Like its precursor, the 6800, the 6502 has very few registers.
(archive) 6502 Games; 1st Ed; Rodnay Zaks; Sybex; 292 pages; 1980; .
(archive) Reference cards 6502 Microprocessor Instant Reference Card; James Lewis; Micro Logic; 2 pages; 1980.
(archive) 6502 Assembly Language Subroutines; 1st Ed; Lance Leventhal and Winthrop Saville; Osborne/McGraw-Hill; 550 pages; 1982; .
(archive) Advanced 6502 Programming; 1st Ed; Rodnay Zaks; John Wiley & Sons; 292 pages; 1982; .
(archive) Machine Language For Beginners - Personal Computer Machine Language Programming For Atari, VIC, Apple, C64, and PET Computers; 1st Ed; Richard Mansfield; Compute! Publications; 350 pages; 1983; .
(archive) Programming the 6502; 4th Ed; Rodnay Zaks; Sybex; 408 pages; 1983; .
(archive) 6502 User's Manual; 1st Ed; Joseph Carr; Reston; 288 pages; 1984; .
(archive) 6502 Assembly Language Programming; 2nd Ed; Lance Leventhal; Osborne/McGraw-Hill; 650 pages; 1986; .
(archive) Programming the 65816 - including the 6502, 65C02, 65802; 1st Ed; David Eyes and Ron Lichty; Prentice Hall; 636 pages; 1986; .
It remains a characteristic of 6502 derivatives to this day. ==See also== List of 6502 assemblers MOS Technology 6502-based home computers Interrupts in 65xx processors Transistor count Apple II accelerators cc65 - 6502 macro assembler and C compiler ==Notes== ==References== ===Citations=== ===Bibliography=== Interview with William Mensch Stanford and the Silicon Valley Project, October 9, 1995.
Available through electronics distributors, as of March 2020, the W65C816S is officially rated for 14 MHz operation. The Western Design Center also designed and produced the 65C802, which was a 65C816 core with a 64-kilobyte address space in a 65(C)02 pin-compatible package.
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