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112-469: MOS Technology's first processor, the 6501 , could be plugged into existing motherboards that used the Motorola 6800 , allowing potential users (i.e. engineers and hobbyists) to get a development system up and running very easily using existing hardware. Motorola immediately sued, forcing MOS to pull the 6501 from the market. Changing the pin layout produced the "lawsuit-friendly" 6502 . Otherwise identical to

224-467: A 74158 . The next major difference was to simplify the registers. To start with, one of the two accumulators was removed. General-purpose registers like accumulators have to be accessed by many parts of the instruction decoder, and thus require significant amounts of wiring to move data to and from their storage. Two accumulators makes many coding tasks easier, but costs the chip design itself significant complexity. Further savings were made by reducing

336-502: A CMOS version, the 65C02 . This continues to be widely used in embedded systems , with estimated production volumes in the hundreds of millions. The 6502 was designed by many of the same engineers that had designed the Motorola 6800 microprocessor family. Motorola started the 6800 microprocessor project in 1971 with Tom Bennett as the main architect. Motorola's engineers could run analog and digital simulations on an IBM 370-165 mainframe computer. The chip layout began in late 1972,

448-432: A computer. This was later spun off to become the magazine Circuit Cellar , focusing on embedded computer applications. Significant articles in this period included the insertion of floppy disk drives into S-100 computers, publication of source code for various computer languages (Tiny C , BASIC , assemblers ), and coverage of the first microcomputer operating system , CP/M . The first four issues were produced in

560-531: 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… The main change in terms of chip size was the elimination of

672-466: A contemporaneous competitor, the Intel 8080 , which likewise has one 8-bit accumulator and a 16-bit program counter, but has six more general-purpose 8-bit registers (which can be combined into three 16-bit pointers) and a larger 16-bit stack pointer. In order to make up somewhat for the lack of registers, the 6502 includes a zero page addressing mode that uses one address byte in the instruction instead of

784-490: A few years of interruption. The Arabic edition also ended abruptly. Many of Byte ' s columnists migrated their writing to personal web sites. One such site was science fiction author Jerry Pournelle 's weblog The View From Chaos Manor derived from a long-standing column in Byte , describing computers from a power user 's point of view. After the closure of Byte magazine, Pournelle's column continued to be published in

896-457: A flaw was very high. In most cases, 90% of such designs were flawed, resulting in a 10% yield. 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. Masks no longer picked up dirt from the wafers and lasted on

1008-415: A follow up is the decision to create BYTE magazine using the facilities of Green Publishing Inc. I will end up with the editorial focus for the magazine; with the business end being managed by Green Publishing. To advertise the new magazine, Green contacted a number of the companies that had been advertising in 73 and asked for their contact lists. He then sent letters out to these people telling them about

1120-399: A greater extent than in many other designs; the two-phase clock (supplying two synchronizations per cycle) could thereby control the machine cycle directly. This design also led to one useful design note of the 6502, and the 6800 before it. Because the chip only accessed memory during a certain part of the clock cycle, and this duration was indicated by the φ2-low clock-out pin, other chips in

1232-439: A magazine dedicated to the newly emerging microcomputer market. In 1974, Carl Helmers published a series of six articles that detailed the design and construction of his "Experimenter's Computer System", a personal computer based on the Intel 8008 microprocessor. In January 1975 this became the monthly ECS magazine with 400 subscribers. Green contacted Helmers and proposed starting a new magazine to be known as Byte. The deal

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1344-447: A party, was a way to share some of the internal wiring to allow the ALU to be reduced in size. Despite their best efforts, the final design ended up being 5 mils too wide. The first 6502 chips were 168 by 183 mils (4.3 mm × 4.6 mm), for an area of 19.8 mm . The original version of the processor had no rotate right (ROR) capability, so the instruction was omitted from

1456-437: A peer of Rolling Stone and Playboy , and others such as David Bunnell of PC Magazine aspired to emulate its reputation and success. It was the only computer publication on the 1981 Folio 400 list of largest magazines. Byte ' s 1982 average number of pages was 543, and the number of paid advertising pages grew by more than 1,000 while most magazines' amount of advertising did not change. Its circulation of 420,000

1568-504: A portfolio of semiconductor patents. Allen-Bradley decided not to fight this case and sold their interest in MOS Technology back to the founders. Four of the former Motorola engineers were named in the suit: Chuck Peddle, Will Mathys, Bill Mensch and Rod Orgill. All were named inventors in the 6800 patent applications. During the discovery process, Motorola found that one engineer, Mike Janes, had ignored Peddle's instructions and brought his 6800 design documents to MOS Technology. In March 1976,

1680-399: A series of switches on the front of the machine to enter data. In order to do anything useful, the user had to enter a small program known as the "bootstrap loader" into the machine using these switches, a process known as booting . Once loaded, the loader would be used to load a larger program off a storage device like a paper tape reader. It would often take upwards of five minutes to load

1792-476: A set of chips that could sell at $ 20 to compete with the recently introduced Intel 4040 that sold for $ 29 in a similar complete chipset. Chips are produced by printing multiple copies of the chip design on the surface of a wafer , a thin disk of highly pure silicon. Smaller chips can be printed in greater numbers on the same wafer, decreasing their relative price. Additionally, wafers always include some number of tiny physical defects that are scattered across

1904-517: A signed 8-bit offset relative to the instruction after the branch; the numerical range −128..127 therefore translates to 128 bytes backward and 127 bytes forward from the instruction following the branch (which is 126 bytes backward and 129 bytes forward from the start of the branch instruction). Accumulator mode operates on the accumulator register and does not need any operand data. Immediate mode uses an 8-bit literal operand. The indirect modes are useful for array processing and other looping. With

2016-553: A single printed circuit board with all the components on one side. It included three main ICs ; the MCS6502 CPU and two MCS6530 Peripheral Interface/Memory Devices. Each MCS6530 comprises a mask programmable 1024 x 8 ROM, a 64 x 8 RAM, two eight-bit bi-directional ports, and a programmable interval timer. The KIM-1 brochure said "1 K BYTE RAM" but it actually had 1152 bytes. The memory was composed of eight 6102 static RAMs (1024 x 1 bits) and

2128-763: A small cash register -like printer. A debug monitor was provided as standard firmware for the AIM, and users could also purchase optional ROM chips with an assembler and a Microsoft BASIC interpreter to choose from. Finally, there was the Synertek SYM-1 variant, which could be said to be a machine halfway between the KIM and the AIM; it had the KIM's small display, and a simple membrane keyboard of 29 keys (hex digits and control keys only), but provided AIM-standard expansion interfaces and true RS-232 (voltage level as well as current loop mode supported). The KIM-1 consisted of

2240-499: A small loudspeaker . Canadian programmer Peter R. Jennings produced what was probably the first game for microcomputers to be sold commercially, Microchess , originally for the KIM-1. As the system became more popular, one of the common additions was the Tiny BASIC programming language . This required an easy memory expansion; "all of the decoding for the first 4 K is provided right on

2352-624: A start which reads like a romantic light opera with an episode or two reminiscent of the Keystone Cops , Byte magazine finally has moved into separate offices of its own." Green was not happy about losing Byte and decided to start a new magazine called Kilobyte . He announced these intentions early, and advertised the upcoming magazine in 73 , with the goal of shipping the first issue in December 1976 (the January 1977 edition). Byte quickly took out

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2464-563: A supplier of electronic components and industrial controls, acquired a majority interest in 1970. The company designed and fabricated custom ICs for customers and had developed a line of calculator chips. After the Mostek efforts fell through, Peddle approached Paivinen, who "immediately got it". On 19 August 1974, Chuck Peddle, Bill Mensch, Rod Orgill, Harry Bawcom, Ray Hirt, Terry Holdt, and Wil Mathys left Motorola to join MOS. Mike Janes joined later. Of

2576-474: A system could access memory during those times when the 6502 was off the bus. This was sometimes known as "hidden access". This technique was widely used by computer systems; they would use memory capable of access at 2 MHz, and then run the CPU at 1 MHz. This guaranteed that the CPU and video hardware could interleave their accesses, with a total performance matching that of the memory device. Because this access

2688-450: A trademark on "KILOBYTE" as the name for a cartoon series in Byte magazine, and threatened to sue for trademark violations. This forced Green to change the name of the new magazine to Kilobaud . There was competition and animosity between Byte Publications and 73 Inc. but both remained in the small town of Peterborough, New Hampshire . In April 1979, owner/publisher Virginia Williamson (née Londner Green) sold Byte to McGraw-Hill . At

2800-496: Is hardwired to memory page $ 01 , i.e. the address range $ 0100 – $ 01FF ( 256 – 511 ). Software access to the stack is done via four implied addressing mode instructions, whose functions are to push or pop (pull) the accumulator or the processor status register. The same stack is also used for subroutine calls via the JSR (jump to subroutine) and RTS (return from subroutine) instructions and for interrupt handling. The chip uses

2912-536: Is a little-endian 8-bit processor with a 16-bit address bus . The original versions were fabricated using an 8 µm process technology chip with a die size of 3.9 mm × 4.3 mm (153 by 168 mils), for a total area of 16.6 mm . The internal logic runs at the same speed as the external clock rate. It featured a simple pipeline; on each cycle, the processor fetches one byte from memory and processes another. This means that any single instruction can take as few as two cycles to complete, depending on

3024-442: 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. When it was introduced in 1975, the 6502 was the least expensive microprocessor on the market by a considerable margin. It initially sold for less than one-sixth

3136-465: Is capable of performing addition and subtraction in binary or binary-coded decimal . Placing the CPU into BCD mode with the SED (set D flag) instruction results in decimal arithmetic, in which $ 99 + $ 01 would result in $ 00 and the carry (C) flag being set. In binary mode ( CLD , clear D flag), the same operation would result in $ 9A and the carry flag being cleared. Other than Atari BASIC , BCD mode

3248-411: The Byte name back when it officially relaunched Byte as Byte.com on July 11, 2011. According to the site, the mission of the new Byte was: ...to examine technology in the context of the consumerization of IT. The subject relates closely to important IT issues like security and manageability. It's an issue that reaches both IT and users, and it's an issue where both groups need to listen carefully to

3360-597: The Commodore PET and Apple II , both released in 1977. It was later used in the Atari 8-bit computers , Acorn Atom , BBC Micro , VIC-20 and other designs both for home computers and business, such as Ohio Scientific and Oric computers . The 6510 , a direct successor of the 6502 with a digital I/O port and a tri-state address bus, was the CPU utilized in the best-selling Commodore 64 home computer. Another important use of

3472-406: The operating system uses most of zero page, leaving only a handful of locations for the user. Addressing modes also include implied (1-byte instructions); absolute (3 bytes); indexed absolute (3 bytes); indexed zero-page (2 bytes); relative (2 bytes); accumulator (1); indirect,x and indirect,y (2); and immediate (2). Absolute mode is a general-purpose mode. Branch instructions use

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3584-445: The stack register from 16 to 8 bits, meaning that the stack could only be 256 bytes long, which was enough for its intended role as a microcontroller. The 16-bit IX index register was split in two, becoming X and Y. More importantly, the style of access changed. In the 6800, IX held a 16-bit address which was offset by an 8-bit number stored with the instruction, and added together. In the 6502 (and most other contemporary designs),

3696-615: The tri-state drivers from the address bus outputs. A three-state bus has states for 1 , 0 and high impedance . The last state is used to allow other devices to access the bus, and is typically used for multiprocessing , or more commonly in these roles, for direct memory access (DMA). While useful, this feature is expensive in terms of on-chip circuitry. The 6502 simply removed this feature, in keeping with its design as an inexpensive controller being used for specific tasks and communicating with simple devices. Peddle suggested that anyone who required this style of access could implement it with

3808-436: The "EXORciser" debugging system, onsite training and field application engineer support. Both Intel and Motorola had initially announced a US$ 360 price for a single microprocessor. The actual price for production quantities was much less. Motorola offered a design kit containing the 6800 with six support chips for US$ 300 . Peddle, who would accompany the salespeople on customer visits, found that customers were put off by

3920-441: The "layout" was a very manual process done with color pencils and vellum paper . The layout consisted of thousands of polygon shapes on six different drawings; one for each layer of the fabrication process. Given the size limits, the entire chip design had to be constantly considered. Mensch and Paivinen worked on the instruction decoder while Mensch, Peddle and Orgill worked on the ALU and registers. A further advance, developed at

4032-567: The 16-bit base address was stored in the instruction, and the 8-bit X or Y was added to it. Finally, the instruction set was simplified, freeing up room in the decoder and control logic. Of the original 72 instructions in the 6800, 56 were implemented. Among those removed were instructions that operated between the 6800's two accumulators, and several branch instructions inspired by the PDP-11 . The chip's high-level design had to be turned into drawings of transistors and interconnects. At MOS Technology,

4144-416: The 5/6 cycle "(indirect),y" mode, the 8-bit Y register is added to a 16-bit base address read from zero page, which is located by a single byte following the opcode. The Y register is therefore an index register in the sense that it is used to hold an actual index (as opposed to the X register in the 6800, where a base address was directly stored and to which an immediate offset could be added). Incrementing

4256-542: The 6500 family was in video games. The first to make use of the processor design was the 1977 Atari VCS, later renamed the Atari 2600 . The VCS used a 6502 variant named the 6507 , which had fewer pins, so it could address only 8  KB of memory. Millions of the Atari consoles would be sold, each with a MOS processor. Another significant use was by the Nintendo Entertainment System and Famicom. The 6502 used in

4368-418: The 6501 appeared in several publications the first week of August 1975. The 6501 would be for sale at Wescon for $ 20 each. In September 1975, the advertisements included both the 6501 and the 6502 microprocessors. The 6502 would cost only $ 25 (equivalent to $ 142 in 2023). When MOS Technology arrived at Wescon, they found that exhibitors were not permitted to sell anything on the show floor. They rented

4480-480: The 6501, it nevertheless had the disadvantage of having no machine in which new users could quickly start using the CPU . Chuck Peddle , leader of the 650x group at MOS (and former member of Motorola's 6800 team), designed the KIM-1 in order to fill this need. The KIM-1 came to market in 1976. While the machine was originally intended to be used by engineers, it quickly found a large audience with hobbyists. A complete system could be constructed for under US$ 500 with

4592-474: The 6502 or variations of the basic design. Soon after the 6502's introduction, MOS Technology was purchased outright by Commodore International , who continued to sell the microprocessor and licenses to other manufacturers. In the early days of the 6502, it was second-sourced by Rockwell and Synertek , and later licensed to other companies. In 1981, the Western Design Center started development of

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4704-454: The 6530s were connected to two connectors on the edge of the board, where they could be used as a serial system for driving a Teletype Model 33 ASR and paper tape reader and punch . One of these connectors also doubled as the power supply connector and included analog lines that could be attached to a cassette tape recorder. Earlier microcomputer systems such as the MITS Altair used

4816-445: The 6800's headlining features was an onboard voltage doubler that allowed a single +5 V supply be used for +5, −5 and +12 V internally, as opposed to other chips of the era like the Intel 8080 that required three separate supply pins. While this feature reduced the complexity of the power supply and pin layout, it still required separate power line to the various gates on the chip, driving up complexity and size. By moving to

4928-416: The 6800. They would not run 6800 software because they had a different instruction set, different registers, and mostly different addressing modes. Rod Orgill was responsible for the 6501 design; he had assisted John Buchanan at Motorola on the 6800. Bill Mensch did the 6502; he was the designer of the 6820 Peripheral Interface Adapter (PIA) at Motorola. Harry Bawcom, Mike Janes and Sydney-Anne Holt helped with

5040-520: The KIM board. All you need to provide is 4 K more of RAM chips and some buffers." The hard part was loading the BASIC from cassette tape —a 15-minute, error-prone ordeal. Rockwell International —who second-sourced the 6502, along with Synertek —released their own microcomputer in one board in 1978, the AIM-65 . The AIM included a full ASCII keyboard, a 20-character 14-segment alphanumeric LED display, and

5152-560: The KIM's memory for the screen storage. The TVT-6 project appeared on the cover on Popular Electronics in July 1977. The complete kit could be ordered from PAiA Electronics for US$ 34.95 . Lancaster expanded this design to do color and simple graphics in The Cheap Video Cookbook . Each bit is represented by three 2.484 ms long tones. The first is always 3700 Hz, the middle is 3700 Hz for "0" or 2400 Hz for "1", and

5264-549: The MacArthur Suite at the St. Francis Hotel and directed customers there to purchase the processors. At the suite, the processors were stored in large jars to imply that the chips were in production and readily available. The customers did not know the bottom half of each jar contained non-functional chips. The chips were $ 20 and $ 25 while the documentation package was an additional $ 10 . Users were encouraged to make photocopies of

5376-559: The NES was a second source version by Ricoh , a partial system on a chip , that lacked the binary-coded decimal mode but added 22 memory-mapped registers and on-die hardware for sound generation, joypad reading, and sprite list DMA . Called 2A03 in NTSC consoles and 2A07 in PAL consoles (the difference being the clock frequency divider ratio and a lookup table for audio sample rates), this processor

5488-624: The Turkish editions of PC World , which was soon renamed as PC Life in Turkey. Nikkei Byte , with the name licensed from McGraw Hill, was the leading computer magazine in Japan, published by Nikkei Business Publications . It continued Pournelle's column in translation as a major feature for years after Byte closed in the U.S. In 1999, CMP revived Byte as a web-only publication, from 2002 accessible by subscription . It closed in 2009. UBM TechWeb brought

5600-663: The XEGS. In the 1980s, a popular electronics magazine Elektor/Elektuur used the processor in its microprocessor development board Junior Computer . The CMOS successor to the 6502, the WDC 65C02 , also saw use in home computers and video game consoles. Apple used it in the Apple II line starting with the Apple IIc and later variants of the Apple IIe and also offered a kit to upgrade older IIe systems with

5712-446: The ability to run a cassette tape for storage, drive the LED display, and run the keypad. As soon as the power was turned on, the monitor would run and the user could immediately start interacting with the machine via the keypad. The KIM-1 was one of the first single-board computers , needing only an external power supply to enable its use as a stand-alone experimental computer. This fact, plus

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5824-582: The account and $ 1/hour for X.25 access. Unlike CompuServe , access at higher speeds was not surcharged. Later, gateways permitted email communication outside the system. By 1990, the magazine was about half an inch (1.25 cm) in thickness and had a subscription price of $ 56/year. Around 1993, Byte began to develop a web presence. It acquired the domain name byte.com and began to host discussion boards and post selected editorial content. Editions were published in Japan , Brazil , Germany , and an Arabic edition

5936-479: The artwork of Robert Tinney . These covers made Byte visually distinctive. However, issues featuring cover stories introducing significant hardware such as the Apple Lisa , Apple Macintosh , IBM PC and Commodore Amiga featured product photographs on the covers. From approximately 1980 to 1985, cartoonist Tom Sloan drew full page multipanel cartoons. They covered various computer/tech related themes. Several of

6048-762: The attendees at the WESCON trade show in San Francisco beginning on September 16, 1975. Peddle was a very effective spokesman and the MOS Technology microprocessors were extensively covered in the trade press. 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

6160-511: The business manager of 73 Inc. since December 1974. She incorporated Green Publishing in March 1975 to take over publication. The first issue of the new magazine was the September 1975 edition. Articles in the first issue included Which Microprocessor For You? by Hal Chamberlin , Write Your Own Assembler by Dan Fylstra and Serial Interface by Don Lancaster . Among the more important articles

6272-459: The chips and documentation, whereas other semiconductor companies only wanted to deal with "serious" customers. For example, Signetics was introducing the 2650 microprocessor and its advertisements asked readers to write for information on their company letterhead. The 6501/6502 introduction in print and at Wescon was an enormous success. The downside was that the extensive press coverage got Motorola's attention. In October 1975, Motorola reduced

6384-467: The circuits, which almost always required a separate external chip that could supply a powerful signal. With the reduced power requirements of depletion-load design, the clock could be moved onto the chip, simplifying the overall computer design. These changes greatly reduced complexity and the cost of implementing a complete system. A wider change taking place in the industry was the introduction of projection masking . Previously, chips were patterned onto

6496-494: The company found the KIM-1 also sold well to hobbyists and tinkerers. The related Rockwell AIM-65 control, training, and development system also did well. The software in the AIM 65 was based on that in the MDT. 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. The 6502 was next used in

6608-594: The cost of competing designs from larger companies, such as the 6800 or Intel 8080 . Its introduction caused rapid decreases in pricing across the entire processor market. Along with the Zilog Z80 , it sparked a series of projects that resulted in the home computer revolution of the early 1980s. Home video game consoles and home computers of the 1970s through the early 1990s, such as the Atari 2600 , Atari 8-bit computers , Apple II , Nintendo Entertainment System , Commodore 64 , Atari Lynx , BBC Micro and others, use

6720-418: The details of their proposed 8-bit microprocessor system with ROM, RAM, parallel and serial interfaces. In early 1974, they provided engineering samples of the chips so that customers could prototype their designs. Motorola's "total product family" strategy did not focus on the price of the microprocessor, but on reducing the customer's total design cost. They offered development software on a timeshare computer,

6832-625: The documents, an inexpensive way for MOS Technology to distribute product information. The preliminary data sheets listed just 55 instructions excluding the Rotate Right (ROR) instruction which was not supported on these early chips. The reviews in Byte and EDN noted the lack of the ROR instruction. The next revision of the layout fixed this problem and the May 1976 datasheet listed 56 instructions. Peddle wanted every interested engineer and hobbyist to have access to

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6944-446: The early computer magazines by larger publishers. By this time the magazine had taken on a more serious journal-like atmosphere and began to refer to itself as "the small systems journal". It became an influential publication; Byte was selected as the medium used by Xerox PARC to publicize Smalltalk in 1981. Like many generalist magazines, Byte suffered in the 1990s due to declining advertising sales. McGraw-Hill's publishing arm

7056-435: The era, the dynamic NMOS 6502 chip is not sequenced by microcode but decoded directly using a dedicated PLA . The decoder occupied about 15% of the chip area. This compares to later microcode-based designs like the Motorola 68000 , where the microcode ROM and decoder engine represented about a third of the gates in the system. Like its precursor, the 6800, the 6502 has very few registers . They include This compares to

7168-615: The first 6800 chips were fabricated in February 1974 and the full family was officially released in November 1974. John Buchanan was the designer of the 6800 chip and Rod Orgill, who later did the 6501, assisted Buchanan with circuit analyses and chip layout. Bill Mensch joined Motorola in June 1971 after graduating from the University of Arizona (at age 26). His first assignment was helping define

7280-508: The high cost of the microprocessor chips. At the same time, these visits invariably resulted in the engineers he presented to producing lists of required instructions that were much smaller than "all these fancy instructions" that had been included in the 6800. Peddle and other team members started outlining the design of an improved feature, reduced size microprocessor. At that time, Motorola's new semiconductor fabrication facility in Austin, Texas ,

7392-410: The home or business user's perspective, Byte covered developments in the entire field of "small computers and software", and sometimes other computing fields such as supercomputers and high-reliability computing . Coverage was in-depth with much technical detail, rather than user-oriented. The company was purchased by McGraw-Hill in 1979, a watershed event that led to the rapid purchase of many of

7504-527: The index and stack registers effectively with several addressing modes , including a fast "direct page" or "zero page" mode, similar to that found on the PDP-8 , that accesses memory locations from addresses 0 to 255 with a single 8-bit address (saving the cycle normally required to fetch the high-order byte of the address)—code for the 6502 uses the zero page much as code for other processors would use registers. On some 6502-based microcomputers with an operating system,

7616-429: The index register to walk the array byte-wise takes only two additional cycles. With the less frequently used "(indirect,x)" mode the effective address for the operation is found at the zero page address formed by adding the second byte of the instruction to the contents of the X register. Using the indexed modes, the zero page effectively acts as a set of up to 128 additional (though very slow) address registers. The 6502

7728-410: The last one is always 2400 Hz. This gives an effective bit rate of 134.2 bit/s. Detection is done through a PLL using LM565. The format of data on the tape is: 100 bytes with the value 0x16 (SYN, Synchronous Idle), one byte with the value 0x2A (*), the record identification number, the start address (two characters for the low byte of address, two characters for the high byte), the end address (in

7840-430: The layout. MOS Technology's microprocessor introduction was different from the traditional months-long product launch. The first run of a new integrated circuit is normally used for internal testing and shared with select customers as "engineering samples". These chips often have a minor design defect or two that will be corrected before production begins. Chuck Peddle's goal was to sell the first run 6501 and 6502 chips to

7952-431: The magazine changed editorial policies. It gradually de-emphasized the do-it-yourself electronics and software articles, and began running product reviews. It continued its wide-ranging coverage of hardware and software, but now it reported "what it does" and "how it works", not "how to do it". The editorial focus remained on home and personal computers . By the early 1980s, Byte had become an "elite" magazine, seen as

8064-410: The new depletion-load design, a single +5 V supply was all that was needed, eliminating all of this complexity. A further advantage was that depletion-load designs used less power while switching, thus running cooler and allowing higher operating speeds. Another practical offshoot is that the clock signal for earlier CPUs had to be strong enough to survive all the dissipation as it traveled through

8176-476: The new design, the cost goal demanded a size goal of 153 by 168 mils (3.9 mm × 4.3 mm), or an area of 16.6 mm . Several new techniques would be needed to hit this goal. Two significant advances arrived in the market just as the 6502 was being designed that provided to be significant cost reductions. The first was the move to depletion-load NMOS . The 6800 used an early NMOS process, enhancement mode, that required three supply voltages. One of

8288-477: The new magazine. This resulted in about 20% of the contacts subscribing, a massive conversion rate. Just prior to planning Byte , Green had a run-in with the Internal Revenue Service . When he told his lawyer that he planned on starting a new magazine, he was advised to put it in someone else's name. He had recently gotten back together with his ex-wife, Virginia Londner Green , who had been listed as

8400-581: The new processor. The Hudson Soft HuC6280 chip used in the TurboGrafx-16 was based on a 65C02 core. The Atari Lynx used a custom chip named "Mikey" designed by Epyx which included a VLSI VL65NC02 licensed cell. The G65SC12 by GTE Microcircuits (renamed California Micro Devices) variant was used in the BBC Master . Some models of the BBC Master also included an additional G65SC102 co-processor. The 6502

8512-459: The now independent MOS Technology was running out of money and had to settle the case. They agreed to drop the 6501 processor, pay Motorola $ 200 ,000 and return the documents that Motorola contended were confidential. Both companies agreed to cross-license microprocessor patents. That May, Motorola dropped the price of a single 6800 microprocessor to $ 35 . By November, Commodore had acquired MOS Technology. With legal troubles behind them, MOS

8624-467: The number of operands that instruction uses. For comparison, the Zilog Z80 required two cycles to fetch memory, and the minimum instruction time was four cycles. Thus, despite the lower clock speeds compared to competing designs, typically in the neighborhood of 1 to 2  MHz , the 6502's performance was competitive with CPUs using significantly faster clocks. This is partly due to a simple state machine implemented by combinational (clockless) logic to

8736-406: The offices of 73 and Wayne Green was listed as the publisher. One day in November 1975 Green came back to the office and found that the Byte magazine staff had moved out and taken the January issue with them. For the February 1976 issue, the company changed its name to Byte Publications. Carl Helmers was a co-owner of Byte Publications. The February issue has a short story about the move; "After

8848-456: The order of 100,000 uses rather than 10. This eliminated step-to-step failures and the high flaw rates formerly seen on complex designs. Yields on CPUs immediately jumped from 10% to 60 or 70%. This meant the price of the CPU declined roughly the same amount and the microprocessor suddenly became a commodity device. MOS Technology's existing fabrication lines were based on the older PMOS technology, they had not yet begun to work with NMOS when

8960-650: The original cartoons are now in the Computer History Museum in Mountain View, California. Around 1985, Byte started an online service called BIX ( Byte Information eXchange) which was a text-only BBS-style site running on the CoSy conferencing software, also used by McGraw-Hill internally. Access was via local dial-in or, for additional hourly charges, the Tymnet X.25 network. Monthly rates were $ 13/month for

9072-489: The original documentation. The next iteration of the design shrank the chip and added the rotate right capability, and ROR was included in revised documentation. MOS would introduce two microprocessors based on the same underlying design: the 6501 would plug into the same socket as the Motorola 6800, while the 6502 re-arranged the pinout to support an on-chip clock oscillator. Both would work with other support chips designed for

9184-549: The peripheral ICs for the 6800 family and later he was the principal designer of the 6820 Peripheral Interface Adapter (PIA). Bennett hired Chuck Peddle in 1973 to do architectural support work on the 6800 family products already in progress. He contributed in many areas, including the design of the 6850 ACIA (serial interface). Motorola's target customers were established electronics companies such as Hewlett-Packard , Tektronix , TRW , and Chrysler . In May 1972, Motorola's engineers began visiting select customers and sharing

9296-580: The price of a single 6800 microprocessor from $ 175 to $ 69 . The $ 300 system design kit was reduced to $ 150 and it now came with a printed circuit board. On November 3, 1975, Motorola sought an injunction in Federal Court to stop MOS Technology from making and selling microprocessor products. They also filed a lawsuit claiming patent infringement and misappropriation of trade secrets. Motorola claimed that seven former employees joined MOS Technology to create that company's microprocessor products. Motorola

9408-406: The purchase of the computer itself for only US$ 245 , and then adding a power supply, a secondhand terminal and a cassette tape drive . Many books were available demonstrating small assembly language programs for the KIM, including The First Book of KIM by Jim Butterfield et al . One demo program converted the KIM into a music box by toggling a software-controllable output bit connected to

9520-458: The relatively low cost of getting started, made it quite popular with hobbyists through the late 1970s. The designer of the TV Typewriter , Don Lancaster , developed a low-cost video display for the KIM-1. The add-on board would display up to 4000 characters on a TV or monitor. A typical configuration would be 16 lines of 32 upper-case only characters. The board had only 10 low-cost ICs and used

9632-434: The requirements of the other: IT may wish to hold off on allowing devices and software onto the network when they haven't been properly tested and can't be properly supported. But the use of these devices in the enterprise has the air of inevitability for a good reason. They make users more productive and users are demanding them. The Byte.com launch editor-in-chief was tech journalist Gina Smith . On September 26, 2011, Smith

9744-484: The right leaders in the Semiconductor Products division." The division was reorganized and the management replaced. The new group vice-president John Welty said, "The semiconductor sales organization lost its sensitivity to customer needs and couldn't make speedy decisions." Peddle began looking outside Motorola for a source of funding for this new project. He initially approached Mostek CEO L. J. Sevin , but

9856-506: The same format), the actual data, one byte with the value 0x2F ("/" character ), a two-byte checksum , and two bytes with the value 0x04 (EOT, End Of Transmission). Each byte of memory is stored as two sequential ASCII characters on tape, for example, hexadecimal B5 in memory (181 decimal) would be stored as two sequential ASCII characters "B" and "5" (42 and 35 hexadecimal). MOS Technology 6501 The MOS Technology 6502 (typically pronounced "sixty-five-oh-two" or "six-five-oh-two")

9968-432: The seventeen chip designers and layout people on the 6800 team, eight left. The goal of the team was to design and produce a low-cost microprocessor for embedded applications and to target as wide as possible a customer base. This would be possible only if the microprocessor was low cost, and the team set the price goal for volume purchases at $ 5 . Mensch later stated the goal was not the processor price itself, but to create

10080-403: The surface of the wafer by placing a mask on the surface of the wafer and then shining a bright light on it. The masks often picked up tiny bits of dirt or photoresist as they were lifted off the chip, causing flaws in those locations on any subsequent masking. With complex designs like CPUs, 5 or 6 such masking steps would be used, and the chance that at least one of these steps would introduce

10192-482: The surface. Any chip printed in that location will fail and has to be discarded. Smaller chips mean any single copy is less likely to be printed on a defect. For both of these reasons, the cost of the final product is strongly dependent on the size of the chip design. The original 6800 chips were intended to be 180 by 180 mils (4.6 mm × 4.6 mm), but layout was completed at 212 by 212 mils (5.4 mm × 5.4 mm), or an area of 29.0 mm . For

10304-411: The system. Peddle responded to the order by informing Motorola that the letter represented an official declaration of "project abandonment", and as such, the intellectual property he had developed to that point was now his. 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

10416-454: The team arrived. Paivinen promised to have an NMOS line up and running in time to begin the production of the new CPU. He delivered on the promise, the new line was ready by June 1975. 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

10528-506: The time, Byte' s paid circulation was 156,000 readers, making it second only to Business Week in the McGraw-Hill's technology magazine portfolio. She remained publisher until 1983 and became a vice president of McGraw-Hill Publications Company. From August 1979, the magazine switched to computerized typesetting, using a Compugraphic system. Shortly after the IBM PC was introduced, in 1981,

10640-549: The tiny program into memory, and a single error while flipping the switches meant that the bootstrap loader would crash the machine. This could render some of the bootstrap code garbled, in which case the programmer had to reenter the whole thing and start all over again. The KIM-1 included a somewhat more complex built-in Terminal Interface Monitor software called TIM that was "contained in 2048 bytes of ROM in two 6530 ROM/RAM/IO arrays". This monitor software included

10752-498: The two 64 byte RAMs of the MCS6530s. In the 1970s memory sizes were expressed in several ways. Semiconductor manufacturers would use a precise memory size such as 2048 by 8 and sometimes state the number of bits (16384). Mini and mainframe computers had various memory widths (8 bits to over 36 bits) so manufacturers would use the term "words", such as 4K words. The early hobbyist computer advertisements would use both "words" and "bytes". It

10864-503: The two needed to address the full 64 KB of memory. This provides fast access to the first 256 bytes of RAM by using shorter instructions. For instance, an instruction to add a value from memory to the value in the accumulator would normally be three bytes, one for the instruction and two for the 16-bit address. Using the zero page reduces this to an 8-bit address, reducing the total instruction length to two bytes, and thus improving instruction performance. The stack address space

10976-467: Was a billion-dollar company with a plausible case and expensive lawyers. On October 30, 1974, Motorola had filed numerous patent applications on the microprocessor family and was granted twenty-five patents. The first was in June 1976 and the second was to Bill Mensch on July 6, 1976, for the 6820 PIA chip layout. These patents covered the 6800 bus and how the peripheral chips interfaced with the microprocessor. Motorola began making transistors in 1950 and had

11088-556: Was announced in both magazines in May. Green's editorial column in the August 1975 issue of 73 started with this item: The response to computer-type articles in 73 has been so enthusiastic that we here in Peterborough got carried away. On May 25th we made a deal with the publisher of a small (400 circulation) computer hobby magazine to take over as editor of a new publication which would start in August ... Byte . The last issue of ECS

11200-494: Was common to see "4096 words", "4K (4096) words" and "4 K bytes". The term KB was unused or very uncommon. The KIM-1 was introduced in the April 1976 issue of BYTE and the advertisement stated "1 K BYTE RAM" and "2048 ROM BYTES". Also included were six 7-segment LEDs (similar to those on a pocket calculator ) and a 24-key calculator-type keypad. Many of the pins of the I/O portions of

11312-588: Was declined. Sevin later admitted this was because he was afraid Motorola would sue them. While Peddle was visiting Ford Motor Company on one of his sales trips, Bob Johnson, later head of Ford's engine automation division, mentioned that their former colleague John Paivinen had moved to General Instrument and taught himself semiconductor design. Paivinen then formed MOS Technology in Valley Forge, Pennsylvania in 1969 with two other executives from General Instrument, Mort Jaffe and Don McLaughlin. Allen-Bradley ,

11424-486: Was every other cycle, there was no need to signal the CPU to avoid using the bus, making this sort of access easy to implement without any bus logic. When faster memories became available in the 1980s, newer machines could use this same technique while running at higher clock rates, the BBC Micro used newer RAM that allowed its CPU to run at 2 MHz while still using the same bus sharing techniques. Like most simple CPUs of

11536-524: Was having difficulty producing MOS chips, and mid-1974 was the beginning of a year-long recession in the semiconductor industry. Also, many of the Mesa, Arizona employees were displeased with the upcoming relocation to Austin. Motorola's Semiconductor Products Division management showed no interest in Peddle's low-cost microprocessor proposal. Eventually Peddle was given an official letter telling him to stop working on

11648-567: Was produced exclusively for Nintendo . 6502 or variants were used in all of Commodore's floppy disk drives for all of their 8-bit computers, from the PET line through the Commodore 128D, including the Commodore 64. 8-inch PET drives had two 6502 processors. Atari used the same 6507 used in the Atari VCS for its 810 and 1050 disk drives used for all of their 8-bit computer line, from the 400/800 through

11760-652: Was published in Jordan. The readership of Byte and advertising revenue were declining when McGraw-Hill sold the magazine to CMP Media , a successful publisher of specialized computer magazines, in May 1998. The magazine's editors and writers expected its new owner to revitalize Byte , but CMP ceased publication with the July 1998 issue, laid off all the staff and shut down Byte ' s rather large product-testing lab. Publication of Byte in Germany and Japan continued uninterrupted. The Turkish edition resumed publication after

11872-420: Was published on 12 May 1975. In June, subscribers were mailed a notice announcing Byte magazine. Helmers wrote to another hobbyist newsletter, Micro-8 Computer User Group Newsletter , and described his new job as editor of Byte magazine: I got a note in the mail about two weeks ago from Wayne Green, publisher of '73 Magazine' essentially saying hello and why don't you come up and talk a bit. The net result of

11984-513: Was seldom used in home-computer applications. BYTE Byte (stylized as BYTE ) was a microcomputer magazine , influential in the late 1970s and throughout the 1980s because of its wide-ranging editorial coverage. Byte started in 1975, shortly after the first personal computers appeared as kits advertised in the back of electronics magazines. Byte was published monthly, with an initial yearly subscription price of $ 10. Whereas many magazines were dedicated to specific systems or

12096-467: Was sold to CMP Media in May 1998, and the new owners immediately laid off almost everyone in the magazine arm, ending publication with the already-complete July edition. The associated website continued to draw 600,000 page views a month, prompting the owners to re-open the magazine in a pure online format in 1999. It continued as an online publication until 2009, when it shut down, only to be revived in 2011 and then shut down for good in 2013. Wayne Green

12208-534: Was still left with the problem of getting developers to try their processor, prompting Chuck Peddle to design the MDT-650 ("microcomputer development terminal") single-board computer . Another group inside the company designed the KIM-1 , which was sold semi-complete and could be turned into a usable system with the addition of a 3rd party computer terminal and compact cassette drive. While it sold well to its intended market,

12320-537: Was the editor and publisher of amateur radio magazine 73 . In late 1974 and throughout 1975, 73 published a number of articles on the use of computers, which resulted in a significant response from the readers. The Altair 8800 was announced in January 1975, sparking off intense interest among those working technical fields, including the amateur radio market. Green knew of the Altair because MITS had previously been an advertiser in 73 . This led Green to begin plans for

12432-487: Was the introduction of the Kansas City standard for storing data on cassette tape , which was used by most machines of the era. It included advertisements from Godbout , MITS , Processor Technology , SCELBI , and Sphere , among others. Until the December 1988 issue, a continuing feature was Ciarcia's Circuit Cellar , a column in which electronic engineer Steve Ciarcia described small projects to modify or attach to

12544-471: Was the third highest of all computer magazines. Byte earned $ 9 million from revenue of $ 36.6 million in 1983, twice the average profit margin for the magazine industry. It remained successful while many other magazines failed in 1984 during economic weakness in the computer industry. The October 1984 issue had about 300 pages of ads sold at an average of $ 6,000 per page. Starting with the December 1975 issue through September 1990, Byte covers often featured

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