A 1973 MOS Technology advertisement highlighting their custom integrated circuit capabilities
Three former General Instrument executives, John Paivinen, Mort Jaffe and Don McLaughlin, formed MOS Technology in Valley Forge, Pennsylvania in 1969. The Allen-Bradley Company was looking to provide a second source for electronic calculators and their chips designed by Texas Instruments (TI). In 1970 Allen-Bradley acquired a majority interest in MOS Technology.
In the early 1970s, TI decided to release their own line of calculators, instead of selling just the chips inside them, and introduced them at a price that was lower than the price of the chipset alone. Many early chip companies were reliant on sales of calculator chips and were wiped out in the aftermath; those that survived did so by finding other chips to produce. MOS became a supplier to Atari, producing a custom single-chip Pong system.
Things changed dramatically in 1975. Several of the designers of the Motorola 6800 left Motorola shortly after its release, after management told them to stop working on a low-cost version of the design. At the time there was no such thing as a pure-play semiconductor foundry, so they had to join a chip-building company to produce their new CPU. MOS was a small firm with good credentials in the right area, the east coast of the US. The team of four design engineers was headed by Chuck Peddle and included Bill Mensch. At MOS they set about building a new CPU that would outperform the 6800 while being similar to it in purpose and much less expensive. The resulting 6501 design was somewhat similar to the 6800, but by using several design simplifications, the 6501 would be up to four times faster.
Mask fixing
Previous CPU designs, like the 6800, were produced using a device known as a contact aligner. This was essentially a complex photocopier, which optically reproduced a CPU design, or "mask", on the surface of the silicon chip. The name "contact" referred to the fact that the mask was placed directly on the surface of the chip, which had the significant disadvantage that it sometimes pulled away materials from the chip, which were then copied to subsequent chips. This caused the mask to become useless after about a dozen copies, and resulted in the vast majority of chips having fatal flaws; for a complex chip like the 6800, only about 10% of the chips would work once the masking process was complete.[1]
In 1974 Perkin-Elmer publicly introduced the Micralign system, the first projection scanner. Instead of placing the mask on the surface of the chip, it held it far from the surface and used highly accurate optics to project the image. Masks now lasted for thousands of copies instead of tens, and the flaw rate of the chips inverted so that perhaps 70% of the chips produced would work. The result was a similar inversion in pricing. The 6800 sold in small lots for $295; with no other changes than using a Micralign, the same design could sell for $42.[1]
The change to the Micralign revealed a further advantage. Previously the masks were mass-produced by photography companies like Kodak, who would make tens of thousands of copies of a master mask, or "reticle", and ship the masks to the aligners by the truckload. This meant that if a flaw was found in the design, it would cost a significant amount of money to fix it, as all the older masks would have to be thrown out. In contrast, with Micralign there was only one mask per aligner, so there was no inherent cost in replacing the mask if need be, although the cost, and especially time, of producing these master masks was considerable.[1]
MOS developed the ability to "fix" its masks after they had been produced.[1] This meant that as flaws in the design were discovered, the masks could be removed from the aligners, fixed, and put back in. This allowed them to rapidly drive out flaws in the original masks.
The company's production lines typically reversed the numbers others were achieving; even the early runs of a new CPU design—what would become the 6502—were achieving a success rate of 70 percent or better. This meant that not only were its designs faster, but they also cost much less as well.
When the 6501 was announced, Motorola launched a lawsuit almost immediately. Although the 6501 instruction set was not compatible with the 6800, it could nevertheless be plugged into existing motherboard designs because it had the same functional pin arrangement and IC package footprint. That was enough to allow Motorola to sue. Allen-Bradley sold back its shares to the founders, sales of the 6501 basically stopped, and the lawsuit would drag on for many years before MOS was eventually forced to pay US$200,000 in fines.
In the meantime MOS had started selling the 6502, a chip capable of operating at 1MHz in September 1975 for a mere US$25. It was nearly identical to the 6501, with only a few minor differences: an added on-chip clock oscillator, a different functional pinout arrangement, generation of the SYNC signal (supporting single-instruction stepping), and removal of data bus enablement control signals (DBE and BA, with the former directly connected to the phase 2 clock instead).[2] It outperformed the more-complex 6800 and Intel 8080, but cost much less and was easier to work with. Although it did not have the 6501's advantage of being able to be used in place of the Motorola 6800 in existing hardware, it was so inexpensive that it quickly became more popular than the 6800, making that a moot point.
Image of the circuit board of a Commodore 64 showing some important MOS Technology circuits: the 6510 CPU (long chip, lower left) and the 6581 SID (right). The production week/year (WWYY) of each chip is given below its name.
The 6502 was so cheap that many people believed it was a scam when MOS first showed it at a 1975 trade show. They were not aware of MOS's masking techniques and when they calculated the price per chip at the current industry yield rates, it did not add up. But any hesitation to buy it evaporated when both Motorola and Intel dropped the prices on their own designs from $179 to $69 at the same show in order to compete. Their moves legitimized the 6502, and by the show's end, the wooden barrel full of samples was empty.[citation needed]
A number of different versions of the basic CPU, known as the 6503 through 6507, were offered in 28-pin packages for lower cost. The various models removed signal or address pins. Far and away the most popular of these was the 6507, which was used in the Atari 2600 and Atari disk drives. The 6504 was sometimes used in printers. MOS also released a series of similar CPUs using external clocks, which added a "1" to the name in the third digit, as the 6512 through 6515. These were useful in systems where the clock support was already being provided on the motherboard by some other source. The final addition was the "crossover" 6510, used in the Commodore 64, with additional I/O ports.
Commodore Semiconductor Group
However successful the 6502 was, the company itself was having problems. At about the same time the 6502 was being released, MOS's entire calculator IC market collapsed, and its prior existing products stopped shipping. Soon they were in serious financial trouble. Another company, Commodore Business Machines (CBM), had invested heavily in the calculator market and was also nearly wiped out by TI's entry into the market. A fresh injection of capital saved CBM, and allowed it to invest in company suppliers in order to help ensure their IC supply would not be upset in this fashion again. Among the several companies were LED display manufacturers, power controllers, and suppliers of the driver chips, including MOS.
In late 1976, CBM, publicly traded on the NYSE with a market capitalization around US$60 million, purchased MOS (whose market cap was around US$12 million) in an all-stock deal. Holders of MOS received a 9.4 percent equity stake in CBM[3][4][5] on the condition that Chuck Peddle would join Commodore as chief engineer. The deal went through, and while the firm basically became Commodore's production arm, they continued using the name MOS for some time so that manuals would not have to be reprinted. After a while MOS became the Commodore Semiconductor Group (CSG). Despite being renamed to CSG, all chips produced were still stamped with the old "MOS" logo until week 22/23 of 1989.[6]
MOS had previously designed a simple computer kit called the KIM-1, primarily to "show off" the 6502 chip. At Commodore, Peddle convinced the owner, Jack Tramiel, that calculators were a dead end, and that home computers would soon be huge.
However, the original design group appeared to be even less interested in working for Jack Tramiel than it had for Motorola, and the team quickly started breaking up. One result was that the newly completed 6522 (VIA) chip was left undocumented for years.
Bill Mensch left MOS even before the Commodore takeover, and moved home to Arizona. After a short stint consulting for a local company called ICE, he set up the Western Design Center (WDC) in 1978. As a licensee of the 6502 line, their first products were bug-fixed, power-efficient CMOS versions of the 6502 (the 65C02, both as a separate chip and embedded inside a microcontroller called the 65C150). But then they expanded the line greatly with the introduction of the 65816, a fairly straightforward 16-bit upgrade of the original 65C02 that could also run in 8-bit mode for compatibility. Since then WDC moved much of the original MOS catalog to CMOS, and the 6502 continued to be a popular CPU for the embedded systems market, like medical equipment and car dashboard controllers.
GMT Microelectronics
After Commodore's bankruptcy in 1994, Commodore Semiconductor Group, MOS's successor, was bought by its former management for about $4.3 million, plus an additional $1 million to cover miscellaneous expenses including a United States Environmental Protection Agency (EPA) license. Dennis Peasenell became CEO. In December 1994, the EPA entered into a Prospective Purchase Agreement (limiting the company's liability in exchange for sharing the costs of cleanup) with GMT Microelectronics. In 1994, the company, operating under the name GMT Microelectronics (Great Mixed-signal Technologies), reopened MOS Technology's original, circa-1970 one-micrometre process fab (semiconductor fabrication plant) in Audubon, Montgomery County, Pennsylvania that Commodore had closed in 1993.[7]
The plant had been on the EPA's National Priorities List of hazardous waste sites since October 4, 1989.[8][9] This was due to a 1978 leak of trichloroethylene (TCE) from an underground 250-gallon concrete storage tank used by Commodore Business Machines in the semiconductor cleaning process.[7] Leaks from the tank had caused the local groundwater to become contaminated with TCE and other volatile organic compounds (VOCs) in 1978.[7] By 1999 GMT Microelectronics had $21 million in revenues and 183 employees working on the site.[citation needed] Announced in March 1999, GMT would have provided foundry services based on TelCom's Bipolar and SiCr (silicon chromium) Thin Film Resistor processes and would have been a licensed alternate source for TelCom's Bipolar based products,[10] with production running at 10,000 5-inch semiconductor wafers per month, producing CMOS, BiCMOS, NMOS, bipolar and SOI (silicon on insulator) devices. In 2000, GMT Microelectronics discontinued operations and abandoned all of its assets at the Commodore Semiconductor Group superfund site.[7]
Chip naming convention
Most of the MOS chips are named according to following rules, which shows used technology (logic gate design):[11]
The Commodore 64, also known as the C64, is an 8-bit home computer introduced in January 1982 by Commodore International. It has been listed in the Guinness World Records as the highest-selling single computer model of all time, with independent estimates placing the number sold between 12.5 and 17 million units. Volume production started in early 1982, marketing in August for US$595. Preceded by the VIC-20 and Commodore PET, the C64 took its name from its 64 kilobytes(65,536 bytes) of RAM. With support for multicolor sprites and a custom chip for waveform generation, the C64 could create superior visuals and audio compared to systems without such custom hardware.
The MOS Technology 6502 is an 8-bit microprocessor that was designed by a small team led by Chuck Peddle for MOS Technology. 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.
The MOS Technology 6510 is an 8-bit microprocessor designed by MOS Technology. It is a modified form of the very successful 6502. The 6510 is widely used in the Commodore 64 (C64) home computer and its variants. It is also used in the Seagate ST-251 MFM harddisk.
The 6800 is an 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the M6800 Microcomputer System that also included serial and parallel interface ICs, RAM, ROM and other support chips. A significant design feature was that the M6800 family of ICs required only a single five-volt power supply at a time when most other microprocessors required three voltages. The M6800 Microcomputer System was announced in March 1974 and was in full production by the end of that year.
The Motorola 6809 ("sixty-eight-oh-nine") is an 8-bit microprocessor with some 16-bit features. It was designed by Motorola's Terry Ritter and Joel Boney and introduced in 1978. Although source compatible with the earlier Motorola 6800, the 6809 offered significant improvements over it and 8-bit contemporaries like the MOS Technology 6502, including a hardware multiplication instruction, 16-bit arithmetic, system and user stack registers allowing re-entrant code, improved interrupts, position-independent code, and an orthogonal instruction set architecture with a comprehensive set of addressing modes.
The 6507 is an 8-bit microprocessor from MOS Technology, Inc. It is a version of their 40-pin 6502 packaged in a 28-pin DIP, making it cheaper to package and integrate in systems. The reduction in pin count is achieved by reducing the address bus from 16 bits to 13 and removing a number of other pins used only for certain applications.
The KIM-1, short for Keyboard Input Monitor, is a small 6502-based single-board computer developed and produced by MOS Technology, Inc. and launched in 1976. It was very successful in that period, due to its low price and easy-access expandability.
Charles Ingerham Peddle was an American electrical engineer best known as the main designer of the MOS Technology 6502 microprocessor, the KIM-1 single-board computer, and its successor, the Commodore PET personal computer, both based on the 6502.
The Commodore Plus/4 is a home computer released by Commodore International in 1984. The "Plus/4" name refers to the four-application ROM-resident office suite ; it was billed as "the productivity computer with software built in".
The VIC (Video Interface Chip), specifically known as the MOS Technology 6560 (NTSC version) / 6561 (PAL version), is the integrated circuit chip responsible for generating video graphics and sound in the VIC-20 home computer from Commodore. It was originally designed for applications such as low cost CRT terminals, biomedical monitors, control system displays and arcade or home video game consoles.
William David Mensch, Jr. is an American electrical engineer born in Quakertown, Pennsylvania. He was a major contributor to the design of the Motorola 6800 8-bit microprocessor and was part of the team led by Chuck Peddle that created the MOS Technology 6502. He also designed the 16-bit successor to the 6502, the 65816.
The VIC-II, specifically known as the MOS Technology 6567/6566/8562/8564, 6569/8565/8566 (PAL), is the microchip tasked with generating Y/C video signals and DRAM refresh signals in the Commodore 64 and Commodore 128 home computers.
The Commodore 65 is a prototype computer created at Commodore Business Machines in 1990–1991. It is an improved version of the Commodore 64, and it was meant to be backwards-compatible with the older computer, while still providing a number of advanced features close to those of the Amiga.
The Television Interface Adaptor (TIA) is the custom computer chip, along with a variant of the MOS Technology 6502 constituting the heart of the 1977 Atari Video Computer System game console. The TIA generates the screen display, sound effects, and reads the controllers. At the time the Atari VCS was designed, even small amounts of RAM were expensive. The chip was designed around not having a frame buffer, instead requiring detailed programming to create even a simple display.
The MOS Technology "Agnus", usually called Agnus, is an integrated circuit in the custom chipset of the Amiga computer. The Agnus, Denise and Paula chips collectively formed the OCS and ECS chipsets.
The MOS Technology 8502 is an 8-bit microprocessor designed by MOS Technology and used in the Commodore 128 (C128). It is an improved version of the MOS 6510 used in the Commodore 64 (C64). It was manufactured using the HMOS process, allowing it to have higher transistor density, and lower cost, while dissipating less heat. The 8502 allows the C128 to run at double the clock rate of the C64 with some limitations.
The MOS Technology 6522 Versatile Interface Adapter (VIA) is an integrated circuit that was designed and manufactured by MOS Technology as an I/O port controller for the 6502 family of microprocessors. It provides two bidirectional 8-bit parallel I/O ports, two 16-bit timers, and an 8-bit shift register for serial communications or data conversion between serial and parallel forms. The direction of each bit of the two I/O ports can be individually programmed. In addition to being manufactured by MOS Technology, the 6522 was second sourced by other companies including Rockwell and Synertek.
The Motorola 6845, or MC6845, is a display controller that was widely used in 8-bit computers during the 1980s. Originally intended for designs based on the Motorola 6800 CPU and given a related part number, it was more widely used alongside various other processors, and was most commonly found in machines based on the Zilog Z80 and MOS 6502.
In integrated circuits, depletion-load NMOS is a form of digital logic family that uses only a single power supply voltage, unlike earlier NMOS logic families that needed more than one different power supply voltage. Although manufacturing these integrated circuits required additional processing steps, improved switching speed and the elimination of the extra power supply made this logic family the preferred choice for many microprocessors and other logic elements.
A video display controller (VDC), also called a display engine or display interface, is an integrated circuit which is the main component in a video-signal generator, a device responsible for the production of a TV video signal in a computing or game system. Some VDCs also generate an audio signal, but that is not their main function. VDCs were used in the home computers of the 1980s and also in some early video picture systems.
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