MOS Technology

Not to be confused withMostek.

This article is about the company. For metal–oxide–semiconductor technology, seeMOSFET.

MOS Technology, Inc.( "MOS" being short forMetal Oxide Semiconductor), later known asCSG (Commodore Semiconductor Group)andGMT Microelectronics,was asemiconductordesign andfabricationcompany based inAudubon, Pennsylvania.It is most famous for its6502microprocessorand various designs forCommodore International's range ofhome computers.

MOS Technology, Inc.

Industry	Semiconductor design and manufacturing
Predecessor	Allen-Bradley
Founded	1969(1969)
Defunct	2001(2001)
Successor	Commodore Semiconductor Group Western Design Center
Headquarters	Audubon, Pennsylvania , United States

History

A 1973 MOS Technology advertisement highlighting their custom integrated circuit capabilities

Three formerGeneral Instrumentexecutives, John Paivinen, Mort Jaffe and Don McLaughlin, formed MOS Technology in Valley Forge, Pennsylvania in 1969. TheAllen-Bradley Companywas looking to provide a second source for electronic calculators and their chips designed byTexas 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 toAtari,producing a custom single-chipPongsystem.

Things changed dramatically in 1975. Several of the designers of theMotorola 6800left 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 apure-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 byChuck Peddleand includedBill Mensch.At MOS they set about building a newCPUthat would outperform the 6800 while being similar to it in purpose and much less expensive. The resulting6501design 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 acontact aligner.This was essentially a complexphotocopier,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.

In 1974Perkin-Elmerpublicly introduced theMicralignsystem, 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 aMicralign,the same design could sell for$42.

The change to the Micralign revealed a further advantage. Previously the masks were mass-produced by photography companies likeKodak,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.

MOS developed the ability to "fix" its masks after they had been produced.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.

6502 family

Main article:MOS Technology 6502

When the 6501 was announced, Motorola launched a lawsuit almost immediately. Although the 6501instruction setwas not compatible with the 6800, it could nevertheless be plugged into existingmotherboarddesigns because it had the same functional pin arrangement andIC packagefootprint. 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 payUS$200,000in fines.

In the meantime MOS had started selling the6502,a chip capable of operating at1MHzin September 1975 for a mereUS$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).It outperformed the more-complex 6800 andIntel 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 aCommodore 64showing some important MOS Technology circuits: the6510 CPU(long chip, lower left) and the6581 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$179to$69at 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.

The 6502 would quickly go on to be one of the most popular chips of its day. A number of companies licensed the 650x line from MOS, includingRockwell International,GTE,Synertek,andWestern Design Center (WDC).

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 the6507,which was used in theAtari 2600and 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 theCommodore 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 calculatorICmarket 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 byTI'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 theirICsupply would not be upset in this fashion again. Among the several companies wereLEDdisplay manufacturers, power controllers, and suppliers of the driver chips, including MOS.

In late 1976, CBM, publicly traded on theNYSEwith amarket capitalizationaroundUS$60 million,purchased MOS (whose market cap was aroundUS$12 million) in an all-stock deal. Holders of MOS received a 9.4 percent equity stake in CBMon 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 theCommodore 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.

MOS had previously designed a simple computer kit called theKIM-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 completed6522 (VIA)chip was left undocumented for years.

Bill Menschleft 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 theWestern Design Center (WDC)in 1978. As a licensee of the 6502 line, their first products were bug-fixed, power-efficientCMOSversions of the 6502 (the65C02,both as a separate chip and embedded inside amicrocontrollercalled the 65C150). But then they expanded the line greatly with the introduction of the65816,a fairly straightforward16-bitupgrade of the original 65C02 that could also run in8-bitmode for compatibility. Since then WDC moved much of the original MOS catalog to CMOS, and the 6502 continued to be a popular CPU for theembedded systemsmarket, like medical equipment and car dashboard controllers.

GMT Microelectronics

After Commodore'sbankruptcyin 1994, Commodore Semiconductor Group, MOS's successor, was bought by its former management for about$4.3 million,plus an additional$1 millionto cover miscellaneous expenses including aUnited 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 nameGMT Microelectronics(Great Mixed-signal Technologies), reopened MOS Technology's original, circa-1970one-micrometreprocess fab (semiconductor fabrication plant) inAudubon,Montgomery County,Pennsylvania that Commodore had closed in 1993.

The plant had been on the EPA's National Priorities List ofhazardous wastesites since October 4, 1989.This was due to a 1978 leak oftrichloroethylene(TCE) from an underground 250-gallon concrete storage tank used byCommodore Business Machinesin the semiconductor cleaning process.Leaks from the tank had caused the local groundwater to become contaminated with TCE and othervolatile organic compounds(VOCs) in 1978.By 1999 GMT Microelectronics had$21 millionin revenues and 183 employees working on the site.Announced in March 1999, GMT would have provided foundry services based on TelCom'sBipolarand SiCr (silicon chromium) Thin Film Resistor processes and would have been a licensed alternate source for TelCom's Bipolar based products,with production running at 10,000 5-inchsemiconductor wafersper month, producingCMOS,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 Groupsuperfundsite.

Chip naming convention

Most of the MOS chips are named according to following rules, which shows used technology (logic gate design):

• NMOS(M65xx)
• CMOS(M65Cxx)
• HMOS(M75xx)
• HMOS-2(M85xx)

Products

• KIM-1– single board computer (kit)/CPU evaluation board, based on 6502
• 4510– CPU (CSG 65CE02) with two CIAs on-chip; 3.45 MHz
• 5719– Gary Gate Array
• 2521 – 8-digit calculator chip
• 2523 – 8-digit calculator chip
• 2529 – Single chip scientific calculator array
• 6501– CPU pin-compatible with Motorola 6800
• 6502– CPU equal to 6501 except no 6800-pin-compatibility
• 65CE02– CPU derived from the 6502
• 6503– CPU with 12 address pins, NMI pin and IRQ pin
• 6504– CPU with 13 address pins and IRQ pin
• 6505– CPU with 12 address pins, IRQ pin and RDY pin.
• 6507– CPU with 13 address pins
• 6508– CPU with 256 B RAM and 8 I/O pins
• 6509– CPU with 20 address pins
• 6510– CPU with clock pins and I/O ports,
• 6520– PIA Peripheral Interface Adapter
• 6522– VIA Versatile Interface Adapter
• 6523/6525– Tri-Port Interface
• 6526/8520/8521 –CIAComplex Interface Adapter
• 6529 –SPI/SPIA Single Port Interface Adapter
• 6530 –RRIOTROM-RAM-I/O Timer
• 6532– RIOT RAM-I/O Timer
• 6540– 2 KiB ROM
• 6545– CRTC CRT Controller
• 6550– 512 byte Static RAM
• 6551– ACIA Asynchronous Communications Interface Adapter
• 6560– VIC Video Interface Chip, (NTSC)
• 6561– VIC Video Interface Chip, (PAL) Revision: -101 / E
• 6562– VIC Video Interface Chip, (NTSC) (6561 supporting 40-column)
• 6564– 80-column video (intended for Colour PET, part of its design used in the MOS 6560/6561)
• 6566– VIC-II (MaxMachine)
• 6567– VIC-II (NTSC) Revision: R56A/R7/R8/R9
• 6569– VIC-II (PAL) Revision: R1/R3/R4/R5 (R1 = only 5 lumas)
• 6570– 6500/1 microcontroller on keyboard PCB in Amiga 500 revision: -036
• 6572– VIC-II (PAL-N)
• 6573– VIC-II (PAL-M)
• 6581/6582/8580 –SIDSound Interface Device
• 7360/8360–TEDText Editing Device (HMOS-I/II)
• 7501– CPU HMOS-I 6502 with 7-bit I/O port
• 8361– AGNUS Address Generator Unit (NTSC)
• 8362– DENISE Display Encoder
• 8364– PAULA Port Audio UART and Logic
• 8367– AGNUS Address Generator Unit (PAL)
• 8370– "Fat" AGNUS Address Generator Unit (NTSC)
• 8371– "Fat" AGNUS Address Generator Unit (PAL)
• 8372–ECSAGNUS Address Generator Unit
• 8373–ECSDENISE Display Encoder
• 8374–AGAALICE Address Generator Unit
• 8375–ECSAGNUS Address Generator Unit
• 8500– CPU HMOS-II Version of 6510
• 8501– CPU HMOS-II 6502 with 7-bit I/O port
• 8502– CPU compatible with 6510 but able to run at 2 MHz
• 8520– CIA (Complex Interface Adapter) 1 MHz 8520 or 2 MHz 8520A-1 in Amiga
• 8551– ACIA Asynchronous Communications Interface Adapter, HMOS-II variant of the 6551
• 8562– VIC-II (NTSC)
• 8563– VDC Video Display Controller
• 8564– VIC-II (NTSC)
• 8565– VIC-II (PAL)
• 8566– VIC-II (PAL)
• 8568– VDC with composite HSYNC, VSYNC, and RDY interrupt
• 8701– clock generator
• 8721– PLA
• 8722– MMU Memory Management Unit
• 8726– REC RAM Expansion Controller
• 8727– DMA Direct Memory Access

External links

• Media related toMOS Technologyat Wikimedia Commons
• Information on MOS' chips and their use in CBM's computers– By Ronald van Dijk
• Documentation for various chips used in Commodore computers
• EPA page on former MOS/CSG/GMT fabrication facility- link validated November 30, 2016.
• On the Edge: The Spectacular Rise and Fall of Commodore(2005), Variant Press. Covers Chuck Peddle, the formation of MOS Technology and corporate history, and the design and promotion of the 6502.