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MOS Technology

Company Pedigree

 Ascendant Companies Descendent Companies
Company Comments Company Comments
Motorola In August of 1974, eight engineering and marketing employees left to join MOS Technology (Bill Mensch, Chuck Peddle) Commodore Business Machines Bought MOS Technology in October 1976 was renamed it,  Commodore Semiconductor Group.

Company Overview

MOS Technology was an existing privately owned company that made calculator chips when Chuck Peddle and Bill Mensch, and the other six Motorola employees joined them in 1974. MOS Technology’s chip manufacturing facility, was located in Norristown, Pennsylvania, bucking the Silicon Valley trend. Chuck Peddle, Bill Mensch and two other designers went right to work on the 6500 series of microprocessors.

The 6500 series began with the 6501. The 6501 was pin compatible with the 6800, but not software compatible. However, it was taken off the market almost immediately because Motorola sued. In 1975, MOS Technology designed the 6502, which was very different than the 6501. The 6502 became the basis for all of MOS Technologies microprocessors. The 6502 found a home in Apple, Atari, Commodore, and NES microcomputers and game consoles. The 6502 dominated the industry in the late seventies and early eighties until the IBM PC and the Intel 8088 “standardized” the industry.

Although the MOS Technology brand lasted for many years, the company’s independence did not. Challenged by the Motorola law suit, MOS agreed to be purchased by Commodore Business Machines (CBM) in 1976. The newly purchased MOS continued to sell chips to others companies, even as Commodore made plans to bring out its own microcomputer (PET, 1977) based on the 6502.

Note:  MOS Technology and Mostek are two different and unrelated companies. Much of the literature on the Web confuses these two companies.

Major Achievements

Development of the 6502 microprocessor
Surviving Motorola’s law suit 🙂

Chip Identification

Chips developed by MOS carry the MOS logo. However, CBM continued to use the MOS brand. Chips made after October of 1976 are actually CBM chips, so the number of “true” MOS chips is quite small. This distinction is rather academic in that MOS technology moved as an intact group into CBM. It is interesting note that while the outside packages carried the MOS brand, within a short time after the purchase the actual chips carried the CBM brand.

MOS Chips

CPU’s 6501, 6502, 6510, 8500, 8502
 Calculator Chips
Special Function MOS Technologies first products were MPS7500 series calculator chips. MOS produced a 4-function calculator chip (MPS7560) of which Commodore was its biggest customer (which led to Commodores interest in MOS Technology.Also see: Calculator IC Information for chips and pin-outs
  General Use Support Chips
Shift Registers  
Sound 6581 – SID
Interfaces 6570, 6522
Communications 6522