The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle for MOS Technology in 1975. Eight-bit CPUs normally use an 8-bit data bus and a 16-bit address bus which means that their Address space is limited to 64 KBs This is not a "natural A microprocessor incorporates most or all of the functions of a Central processing unit (CPU on a single Integrated Electronics engineer Chuck Peddle is mostly known as the main designer of the MOS Technology 6502 microprocessor MOS Technology Inc, also known as CSG (Commodore Semiconductor Group, was a semiconductor design and fabrication company based in Norristown Pennsylvania Year 1975 ( MCMLXXV) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar. When it was introduced, it was the least expensive full-featured CPU on the market by a considerable margin, costing less than one-sixth the price of competing designs from larger companies such as Motorola and Intel. Motorola Inc ( is an American, multinational Fortune 100, Telecommunications company based in Schaumburg Illinois. It was nevertheless faster than most of them, and, along with the Zilog Z80, sparked a series of computer projects that would eventually result in the home computer revolution of the 1980s. The Zilog Z80 is an 8-bit Microprocessor designed and sold by Zilog from July 1976 onwards A home computer was a class of Personal computer entering the market in 1977 and becoming common during the 1980s The 6502 design was originally second-sourced by Rockwell and Synertek and later licensed to a number of companies; it is still made for embedded systems. In the Electronics industry a second source is a company that is licensed to manufacture and sell components originally designed by another company (the first source Rockwell International was the ultimate incarnation of a series of companies under the sphere of influence of Willard Rockwell, who had made his fortune after the invention and Synertek Inc was an American Semiconductor manufacturer founded in 1973 as a Masked ROM house whose product range branched into a broad offering of An embedded system is a special-purpose Computer system designed to perform one or a few dedicated functions often with Real-time computing constraints

A MOS 6502 processor in a DIP-40 plastic package. In Microelectronics, a dual in-line package (DIP, sometimes called a DIL package is an electronic device package with a rectangular housing and two parallel rows

History and use

The 6502 was designed primarily by the same engineering team that had designed the Motorola 6800. The 6800 is an 8-bit Microprocessor produced by Motorola and released shortly after the Intel 8080 in late 1974 After quitting Motorola en masse, they quickly designed the 6501, a completely new processor that was pin-compatible with the 6800 (that is, it could be plugged into motherboards designed for the Motorola processor, although its instruction set was different). Motorola Inc ( is an American, multinational Fortune 100, Telecommunications company based in Schaumburg Illinois. The 6501 is an Eight-bit Microprocessor, the first sold by MOS Technology. A motherboard is the central or primary Printed circuit board (PCB making up a complex electronic system such as a modern Computer or Laptop Motorola sued immediately, and MOS agreed to stop producing the 6501 and went back to the drawing board.

The result was the "lawsuit-compatible" 6502, which was by design unusable in a 6800 motherboard. Motorola had no objection. However, this left MOS with the problem of getting developers to try their processor, so engineer Chuck Peddle designed the KIM-1 single-board computer. Electronics engineer Chuck Peddle is mostly known as the main designer of the MOS Technology 6502 microprocessor The KIM-1, short for K eyboard I nput M onitor, was a small 6502 -based Microcomputer kit developed and produced by MOS Much to their surprise, the KIM-1 sold well to hobbyists and tinkerers as well as to the engineers it was intended for. The related Rockwell AIM 65 control/training/development system also did well. The Rockwell AIM-65 computer was a development computer based on the MOS Technology 6502 microprocessor introduced in 1976. Another roughly similar product was the Synertek SYM-1. The SYM-1 was a single board "trainer" computer produced by Synertek circa 1978

Apple IIe

The 6502 was introduced at $25 in September 1975, when the 6800 and Intel 8080 were selling for $179. The Apple IIe is the third model in the Apple II series of personal computers produced by Apple Computer. The Intel 8080 was an early Microprocessor designed and manufactured by Intel. ^[1] At first many people thought the new chip's price was a hoax or a mistake, but shortly both Motorola and Intel had dropped their chips to $79. ^[2] These price reductions actually legitimized the 6502, which started selling by the hundreds.

One of the first "public" uses for the design was the Apple I computer, introduced in 1976. The Apple I, also known as the Apple-1, was an early Personal computer. The 6502 was next used in the Commodore PET and the Apple II. The PET ( P ersonal E lectronic T ransactor) was a home -/ Personal computer produced by Commodore starting in 1977 It was later used in the Atari home computers, the BBC Micro family, the Commodore VIC-20 and a large number of other designs both for home computers and business, such as Ohio Scientific. The Atari 8-bit family is a series of 8-bit Home computers manufactured from 1979 to 1992 The VIC-20 ( Germany: VC-20; Japan: VIC-1001) is an 8-bit Home computer which was sold by Commodore Business Machines Ohio Scientific Inc (also known as Ohio Scientific Instruments) was a United States Computer Company that built and marketed computers from

Commodore 64

The 6510, a direct successor of the 6502 with a digital I/O port and a three-state address bus, was the CPU utilized in the Commodore 64 home computer. The MOS Technology 6510 is a Microprocessor designed by MOS Technology Inc In digital Electronics three-state, tri-state, or 3-state logic allows output ports to have a value of logical 0 1 or Hi-Z (Commodore's disk drive, the 1541, had a processor of its own—it too was a 6502. Commodore64 fdd1541 backjpg|thumb|325px|Back panel view of the Commodore 1541 disk drive )

Atari 2600

Another important use of the 6500 family was in video games. The Atari 2600 is a Video game console released in October 1977 The first to make use was the Atari 2600 videogame console. The Atari 2600 is a Video game console released in October 1977 The 2600 used an offshoot of the 6502 called the 6507, which had fewer pins and, as a result, could address only 8 KB of memory. The 6507 is an 8-bit Microprocessor from MOS Technology Inc It is a "cut down" version of their popular 6502. A kilobyte (derived from the SI prefix Kilo -, meaning 1000 is a unit of Information or Computer storage equal to either 1024 Millions of the Atari consoles would be sold, each with a MOS processor. Another significant use was by the Nintendo Famicom, a Japanese video game console. The Nintendo Entertainment System (often abbreviated as NES or simply Nintendo) is an 8-bit Video game console that was released by For a topic outline on this subject see List of basic Japan topics. Its international equivalent, the Nintendo Entertainment System, also used the processor. The Nintendo Entertainment System (often abbreviated as NES or simply Nintendo) is an 8-bit Video game console that was released by The 6502 used in the NES was a second source version by Ricoh, a partial system-on-a-chip, that lacked a binary-coded decimal mode but added 22 memory-mapped registers for sound generation, joypad reading, and sprite list DMA. In the Electronics industry a second source is a company that is licensed to manufacture and sell components originally designed by another company (the first source ( or Ricoh, is a Japanese company that was established on 6 February 1936 as Riken Kankoshi Co System-on-a-chip or system on chip ( SoC or SOC) refers to integrating all components of a Computer or other electronic System In Computing and electronic systems binary-coded decimal ( BCD) is an encoding for decimal numbers in which each digit is represented by its own binary In Computer graphics, a sprite (also known by other names see Synonyms below is a two-dimensional/three-dimensional Image or Animation that Direct memory access ( DMA) is a feature of modern Computers and Microprocessors that allows certain hardware subsystems within the computer to access system Called 2A03 in NTSC consoles and 2A07 in PAL consoles (the difference being the memory divider ratio and a lookup table for audio sample rates), this processor was produced exclusively for Nintendo. The Ricoh 2A03 or RP2A03 ( NTSC version / Ricoh 2A07 or RP2A07 ( PAL version is the 8-bit Microprocessor in NTSC ( National Television System Committee) is the Analog television system used in the United States, Canada, Japan, Mexico The Ricoh 2A03 or RP2A03 ( NTSC version / Ricoh 2A07 or RP2A07 ( PAL version is the 8-bit Microprocessor in PAL, short for Phase Alternating Line, is a colour -encoding system used in Broadcast television systems in large parts of the world A Memory divider is a ratio which is used to determine the operating clock Frequency of Computer memory in accordance with Front Side Bus frequency if is a Multinational corporation headquartered in Kyoto Japan founded on

Even as of 2006, some universities, including the Eindhoven University of Technology, the Netherlands, University of Tasmania, the University of Applied Sciences in Cologne, Germany, University of Exeter in Devon, England, Carleton College, Hull University, Matthew Boulton College, University of Brescia in Italy and Universidad APEC in Santo Domingo, Dominican Republic still use the processor to teach assembly language, computer architecture and digital integrated systems. The University of Tasmania (also abbreviated as UTAS UTas or Tas Uni is an Australian University, with three campuses in Tasmania. A vocational university (professional university or college of higher vocational studies is an institution of Higher education and sometimes Research, which Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. The University of Exeter (usually abbreviated as Exon for post-nominals) is a University in the South West of Devon is a large county in the South West of England. The county is also referred to as Devonshire, but that is an entirely unofficial name England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland This article is about Carleton College in Northfield Minnesota The University of Hull, also known as Hull University, is an English University, founded in 1927 located in Hull (or Kingston upon Hull) a Matthew Boulton College is a Further and Higher Education college situated in the Eastside of Birmingham, West Midlands. Brescia ( Lombard: Brèsa) is a city in the region of Lombardy in northern Italy. Italy (Italia officially the Italian Republic, (Repubblica Italiana is located on the Italian Peninsula in Southern Europe, and on the two largest Universidad APEC ( UNAPEC) is a University in Santo Domingo, Dominican Republic. Santo Domingo de Guzmán (known as Santo Domingo population 2084852 (Metro (2003 estimated 2253437 (Metro in 2006 is the Capital and largest city in the The Dominican Republic ( Spanish: República Dominicana;) is a nation located in the Caribbean region and shares the island of Hispaniola with

Technical description

The 6502 is an 8-bit processor with a 16-bit address bus. Eight-bit CPUs normally use an 8-bit data bus and a 16-bit address bus which means that their Address space is limited to 64 KBs This is not a "natural An address bus is a Computer bus, controlled by CPUs or DMA -capable Peripherals for specifying the Physical addresses of computer The internal logic runs at the same speed as the external clock rate, but despite the slow clock speeds (typically in the neighborhood of 1 or 2 MHz), the 6502's performance was actually competitive with other CPUs using significantly faster clocks. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. This is partly due to a simplistic state machine implemented by combinatorial (clockless) logic to a greater extent than in many other designs; the two phase clock (supplying two synchronizations per cycle) can thereby control the whole machine-cycle directly. Like most simple CPUs of the era, the dynamic NMOS 6502 chip was not sequenced by a microcode ROM but used a PLA (which occupied about 15% of the chip area) for instruction decoding and sequencing. A programmable logic array (PLA is a programmable device used to implement combinational Logic circuits. Like most typical eight-bit microprocessors, the chip does some limited overlapping of fetching and execution.

The low clock frequency moderated the speed requirement of memory and peripherals attached to the CPU, as only about 50% of the clock cycle was available for memory access (due to the asynchronous design, this percentage varied strongly among chip versions). This was critical at a time when affordable memory had access times in the range 450-250ns. The original NMOS 6502 was minimalistically engineered and efficiently manufactured and therefore cheap—an important factor in getting design wins in the very price-sensitive game console and home computer markets.

6502 Pin configuration (40-Pin DIP)

Like its precursor, the Motorola 6800 (but unlike Intel 8080 and similar microprocessors) the 6502 has very few registers. In Microelectronics, a dual in-line package (DIP, sometimes called a DIL package is an electronic device package with a rectangular housing and two parallel rows Motorola Inc ( is an American, multinational Fortune 100, Telecommunications company based in Schaumburg Illinois. The 6800 is an 8-bit Microprocessor produced by Motorola and released shortly after the Intel 8080 in late 1974 The Intel 8080 was an early Microprocessor designed and manufactured by Intel. In Computer architecture, a processor register is a small amount of storage available on the CPU whose contents can be accessed more quickly than storage At the time the processor was designed, small bipolar memories were relatively fast, so it made sense to rely on RAM instead of wasting expensive NMOS chip area on CPU-registers.

The 6502's registers included one 8-bit accumulator register (A), two 8-bit index registers (X and Y), an 8-bit processor status register (P), an 8-bit stack pointer (S), and a 16-bit program counter (PC). In a Computer 's central processing unit ( CPU) an accumulator is a register in which intermediate arithmetic and logic results are stored An index register in a computer's CPU is a Processor register used for modifying Operand addresses during the run of a program typically for doing vector/ A status register (also flag register or condition code register (CCR) is a collection of flag Bits for a processor. In Computer science, a stack is an Abstract data type and Data structure based on the principle of Last In First Out (LIFO The program counter, or shorter PC (also called the instruction pointer, part of the instruction sequencer in some Computers is a register in The subroutine call/scratchpad stack's address space was hardwired to memory page $01, i. e. the address range $0100–$01FF (256–511). Software access to the stack was done via four implied addressing mode instructions whose functions were to push or pop (pull) the accumulator or the processor status register. The same stack was also used for subroutine calls via the JSR (Jump to Subroutine) and RTS (Return from Subroutine) instructions, and for interrupt handling. In Computing, an interrupt is an asynchronous signal from hardware indicating the need for attention or a synchronous event in software indicating the need for a change

The chip used 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 accessed memory locations from address 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 used the zero page much as code for other processors would have used registers. Addressing modes are an aspect of the Instruction set architecture in most Central processing unit (CPU designs The zero page is the series of Memory addresses at the absolute beginning of a Computer 's Address space; that is the page whose starting address is zero The PDP-8 was the first successful commercial Minicomputer, produced by Digital Equipment Corporation (DEC in the 1960s On some 6502-based microcomputers with an operating system, the OS would use most of zero page, leaving only a handful of locations for the user.

Addressing modes also included 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). Addressing modes are an aspect of the Instruction set architecture in most Central processing unit (CPU designs Absolute mode was a general-purpose mode. Branch instructions used 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 used the accumulator as an effective address, and did not need any operand data. In Mathematics, an operand is one of the inputs (arguments of an Operator. Immediate mode used an 8-bit literal operand.

The indirect modes were useful for array processing and other looping. In Computer science an array is a Data structure consisting of a group of elements that are accessed by indexing. With the 5/6 cycle "(indirect),y" mode, the 8-bit Y register was added to a 16-bit base address in zero page, located by a single byte following the opcode. As the resulting address could be anywhere in the 16-bit memory range, the Y register was a true index register, as opposed to the 6800, which had one 16-bit address register. Incrementing the index register to walk the array byte-wise took only two additional cycles. With the less frequently used "(indirect,x)" mode the effective address for the operation was 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 acted as a set of 128 additional (though very slow) address registers.

A Byte magazine article once referred to the 6502 as "the original RISC processor," due to its efficient, simplistic, and nearly orthogonal instruction set (most instructions work with most addressing modes), as well as its 256 zero-page "registers". Byte magazine was an influential Microcomputer magazine in the late 1970s and throughout the 1980s because of its wide-ranging editorial coverage Orthogonal instruction set is a term used in Computer engineering. The 6502 is technically not a RISC design however, as arithmetic operations can read any memory cell (not only zero-page), and some instructions (inc, rol etc. ) even modify memory contrary to the basic load/store philosophy of RISC. Furthermore, orthogonality is equally often associated with "CISC". Orthogonal instruction set is a term used in Computer engineering. However the 6502 performed reasonably well compared to other contemporaneous processors such as the Z80, which used a much faster clock rate, and the 6502 has been credited as being inspirational to RISC processors such as the ARM. The ARM architecture (previously the Advanced RISC Machine, and prior to that Acorn RISC Machine) is a 32-bit RISC processor architecture ^[3]

See the Hello world! article for a simple but characteristic example of 6502 assembly language. See the terminology section below for information regarding inconsistent use of the terms assembly and assembler

Detailed behavior

The processor's non-maskable interrupt input is edge sensitive, which means that if the source of an NMI holds the line low NMI's are effectively disabled. A non-maskable interrupt ( NMI) is a computer processor Interrupt that can not be ignored by standard interrupt masking techniques in the system A non-maskable interrupt ( NMI) is a computer processor Interrupt that can not be ignored by standard interrupt masking techniques in the system

The simultaneous assertion of the NMI (non-maskable) and IRQ (maskable) hardware interrupt lines causes IRQ to be ignored. However, if the IRQ line remains asserted after the servicing of the NMI, the processor will immediately respond to IRQ, as IRQ is level-sensitive. Thus a sort of built-in interrupt priority was established in the 6502 design.

Dubious features

The original 6502 and its NMOS derivatives are noted for having a variety of undocumented instructions, which vary from one chip manufacturer to the next. An Illegal Opcode, also called an Undocumented Instruction, is an instruction to a CPU that is not mentioned in any official documentation released by the CPU's designer The 6502's instruction decoding is implemented in a hardwired logic array (similar to a programmable logic array) which is only defined for 151 of the 256 available opcodes. To execute instructions a Computer 's Processor must generate the control signals used to perform the processor's actions in the proper sequence A programmable logic array (PLA is a programmable device used to implement combinational Logic circuits. In computer technology an opcode ( op eration code) is the portion of a Machine language instruction that specifies the operation to be performed The remaining 105 trigger strange and hard-to-predict actions (e. g. , immediately crashing the processor, performing several valid instructions at once, or simply doing nothing at all). Eastern House Software developed the "Trap65", a device that plugged between the processor and its socket to convert (trap) unimplemented opcodes into BRK (software interrupt) instructions. In 6502 assembly language programming BRK is an Opcode that causes a Software interrupt or trap. Some programmers utilized this feature to extend the 6502's instruction set by providing functionality for the unimplemented opcodes with specially written software intercepted at the BRK instruction's 0xFFFE vector. In 6502 assembly language programming BRK is an Opcode that causes a Software interrupt or trap. All of the undefined opcodes have been replaced by NOP instructions in the 65C02 CMOS version (although with varying byte sizes and execution times). In Computer science NOP or NOOP (short for N o OP eration) is an Assembly language instruction sequence of programming The Western Design Center WDC 65C02 Microprocessor is an upgraded CMOS version of the popular NMOS -based MOS Technology 6502 Complementary metal–oxide–semiconductor ( CMOS) (pronounced "see-moss" siːmɔːs ˈsiːmɒs is a major class of Integrated circuits CMOS technology

The 6502's memory indirect jump instruction, JMP (<address low-word>), is partially broken. An indirect branch (also known as a computed jump, indirect jump and register-indirect jump is a type of program control instruction present If <address low-word> was hex xxFF (i. In Mathematics and Computer science, hexadecimal (also base -, hexa, or hex) is a Numeral system with a e. any word ending in FF), the processor would not jump to the address stored in xxFF and xxFF+1, but rather the one in xxFF and xx00. This defect continued through the entire NMOS line, but was fixed in the CMOS derivatives. Complementary metal–oxide–semiconductor ( CMOS) (pronounced "see-moss" siːmɔːs ˈsiːmɒs is a major class of Integrated circuits CMOS technology

The N (result negative), V (sign bit overflow) and Z (result zero) status flags are not valid when performing arithmetic operations while the processor is in BCD mode, as these flags reflect the binary, not BCD, result. A status register (also flag register or condition code register (CCR) is a collection of flag Bits for a processor. In Computing and electronic systems binary-coded decimal ( BCD) is an encoding for decimal numbers in which each digit is represented by its own binary This limitation was removed in the CMOS derivatives. Complementary metal–oxide–semiconductor ( CMOS) (pronounced "see-moss" siːmɔːs ˈsiːmɒs is a major class of Integrated circuits CMOS technology Therefore, this feature may be used to cleanly distinguish CMOS from NMOS CPU versions without using any illegal opcodes ([1]).

If the processor happens to be in BCD mode when a hardware interrupt occurs it will not revert to binary mode. This quirk could result in hard-to-solve bugs in the interrupt service routine if it failed to clear BCD mode before performing any arithmetic operations. For example, the Commodore 64's kernel did not correctly handle this processor characteristic, requiring that IRQs be disabled or revectored during BCD math operations. In Computer science, the kernel is the central component of most computer Operating systems (OS This issue was addressed in the CMOS derivatives as well.

The 6502 instruction set includes BRK (opcode $00), which is technically a software interrupt (similar in spirit to the SWI mnemonic of the 6800). In 6502 assembly language programming BRK is an Opcode that causes a Software interrupt or trap. In Computing, an interrupt is an asynchronous signal from hardware indicating the need for attention or a synchronous event in software indicating the need for a change The 6800 is an 8-bit Microprocessor produced by Motorola and released shortly after the Intel 8080 in late 1974 BRK is most often used to interrupt program execution and start a machine code monitor for testing and debugging during software development. In 6502 assembly language programming BRK is an Opcode that causes a Software interrupt or trap. A machine code monitor (aka Machine language monitor is software built into or separately available for various computers allowing the user to enter commands to view It could also be used to route program execution using a simple jump table (analogous to the manner in which the 8088 and derivatives handle software interrupts by number). The Intel 8088 is an Intel X86 Microprocessor based on the 8086, with 16- Bit registers and an 8-bit external Data bus Unfortunately, if a hardware interrupt occurs at the same time the processor is fetching a BRK instruction, the NMOS version of the processor will fail to execute BRK and instead proceed as if only a hardware interrupt had occurred. In Computing, an interrupt is an asynchronous signal from hardware indicating the need for attention or a synchronous event in software indicating the need for a change In 6502 assembly language programming BRK is an Opcode that causes a Software interrupt or trap. In 6502 assembly language programming BRK is an Opcode that causes a Software interrupt or trap. This fault was corrected in the CMOS implementation of the processor.

The JSR (call subroutine) instruction pushes the address of the last byte of the call instruction on to the stack, not the expected address of the next instruction. The RTS (return) instruction pulls the return address off the stack and increments it before placing it into the program counter, resulting in automatic compensation for this design quirk. The program counter, or shorter PC (also called the instruction pointer, part of the instruction sequencer in some Computers is a register in This characteristic would go unnoticed unless you pulled the return address to pick up parameters in the code stream (a common 6502 programming idiom). It remains a characteristic of 6502 derivatives to this day.

16-bit derivatives

The Western Design Center designed and produced the 65C816 processor, a 16-bit successor to the 65C02, as well as a hybrid offshoot called the 65C802 which was a 65C816 core with a 64 KB address space in a 65(C)02 pin-compatible package—it could be plugged into a 6502 board and would function as a 65C02, or it could be configured via software to expose its 16 bit accumulator and index registers. The Western Design Center (WDC, located in Mesa Arizona, USA, is a company developing and manufacturing MOS 65xx -based Microprocessors The WDC 65816 (also 65C816) a 16-bit Microprocessor CPU developed by the Western Design Center (WDC, is an expanded and compatible The WDC 65816 (also 65C816) a 16-bit Microprocessor CPU developed by the Western Design Center (WDC, is an expanded and compatible In a Computer 's central processing unit ( CPU) an accumulator is a register in which intermediate arithmetic and logic results are stored An index register in a computer's CPU is a Processor register used for modifying Operand addresses during the run of a program typically for doing vector/ Few 65C802 parts were sold, and the chip is no longer produced. The 65C816 is still widely used, both as a discrete processor and as the core of a microcontroller. An electronic component is a basic electronic element usually packaged in a discrete form with two or more connecting leads or metallic pads A microcontroller (also MCU or µC is a functional Computer system-on-a- chip.

Mitsubishi (now Renesas Technology) made a line of 16-bit microcontrollers with an architecture very similar to the 65816, though it was not 100% compatible. The, Mitsubishi Group of Companies, or Mitsubishi Companies is a Japanese conglomerate consisting of a range of autonomous businesses which share the Mitsubishi is a Japanese semiconductor manufacturer They are based in Tokyo and have manufacturing design and sales operations in around 20 countries with about 26200 employees worldwide

Synertek published a data sheet and application notes on the SY6516, a 16-bit derivative of the 6502, but the part was never introduced. Synertek Inc was an American Semiconductor manufacturer founded in 1973 as a Masked ROM house whose product range branched into a broad offering of

32-bit derivatives

The Western Design Center at one time claimed to be developing a W65T32 Terbium, a compatible 32-bit follow-up to the W65C816. The Terbium was named after the 65^th element as 65 is the prefix to all of WDC's microprocessor number identifiers. Terbium (ˈtɝbiəm is a Chemical element with the symbol Tb and Atomic number 65 The chip would have had a 32-bit address bus, a 16-bit data bus, and a variable length instruction set.

Acceleration

Many users of 1 MHz 6502-based systems soon wished their computers could go faster. A number of companies sold replacement hardware to speed up those systems. Generally, 6502 system accelerators were based on:

• 6502 or 65C02 chips running at a faster clock rate
• 65C816 chips in 6502 emulation mode, running at a much faster clock rate (up to 20 MHz)
• 4 MHz and 8 MHz Zip Chip processors, made by Zip Technology, and 10 MHz Rocket Chips, made by Bits and Pieces, all using onboard cache RAM and proprietary glue logic to speed up processing while remaining compatible with a 1 MHz motherboard. The Western Design Center WDC 65C02 Microprocessor is an upgraded CMOS version of the popular NMOS -based MOS Technology 6502 The WDC 65816 (also 65C816) a 16-bit Microprocessor CPU developed by the Western Design Center (WDC, is an expanded and compatible The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. In Computer science, a cache (kæʃ like "cash") is a collection of data duplicating original Zip Technology's patent #4,794,523 eventually forced Bits and Pieces to cease manufacturing of the Rocket Chip.

6502 in popular culture

In the science fiction movie The Terminator (1984), starring Arnold Schwarzenegger, the audience at one point is treated to a view through the T-800 Model-101 robot character's eye/camera display with some 6502 assembly/machine code program fragments scrolling down the screen. The Terminator is a 1984 science fiction / Action film directed and co-written by James Cameron. Arnold Alois Schwarzenegger ( German ˌaɐnɔlt aloʏs ˈʃvaɐtsənɛɡɐ born July 30 1947 is an Austrian American Bodybuilder, Actor Computer vision is the science and technology of machines that see In Computer graphics, Movies, Television, and other kinetic displays scrolling is sliding text images or video across a monitor or display Also shown is the output from a run of an Apple II checksum program called KEY PERFECT 4. A checksum is a form of Redundancy check, a simple way to protect the integrity of data by detecting errors in data that are sent through space ( Telecommunications 0, published in Nibble magazine. Nibble was a magazine for Apple II Computer users with a focus on hobbyist programming.

Bender, a fictional android "industrial robot" manufactured in 2998 AD, and a main character in the animated TV series Futurama, was revealed to have a 6502 as his "brain," in the episode "Fry and the Slurm Factory. Bender, full name Bender Bending Rodríguez, designated Bending Unit 22, is a fictional Robot character in the Animated television series Futurama is an Emmy Award -winning animated American sitcom created by Matt Groening, and developed by Groening and " Fry and the Slurm Factory " is the thirteenth Episode of the first production season of Futurama. "

See also

• Lisa assembler
• MOS Technology 6502-based

References

• Leventhal, Lance A. (1986). 6502 Assembly Language Programming 2nd Edition. Osborne/McGraw-Hill. ISBN 0-07-881216-X.
• Leventhal, Lance A. (1982). 6502 Assembly Language Subroutines. Osborne/McGraw-Hill. ISBN 0-931988-59-4.
• Mansfield, Richard (1983). Machine Language For Beginners. Personal Computer Machine Language Programming For The Atari, VIC, Apple, Commodore 64, And PET/CBM Computers (or, Machine Language Programming For BASIC Language Programmers). Greensboro, North Carolina: Compute! Publications, Inc. Copyright © 1983, Small System Services, Inc. ISBN 0-942386-11-6.
• Zaks, Rodnay (1983). Rodnay Zaks (born 10 February 1946 Paris) is a prolific French-born American author of books on computer programming including the seminal Programming the Z80 Programming the 6502 (Fourth Edition). Sybex, Inc. ISBN 0-89588-135-7.
• Zaks, Rodnay (1982). Advanced 6502 Programming. Sybex, Inc. ISBN 0-89588-089-X.
• Fylstra, Daniel (November 1975). "Son of Motorola (or the $20 CPU Chip)". BYTE 1 (3): 56-62. Peterborough NH: Green Publishing.   A comparison of the Motorola M6800 and the MOS Technology MCS6501/MCS6502 microprocessors. It was written in August 1975, about a month before the 6500 family was introduced at the WESCON trade show in San Francisco CA. , (September 16-19, 1975)
• Sugarman, Robert (August 25, 1975), “Does the Country Need a Good $20 Microprocessor?”, Electrical Engineering Times: 25, <http://www.commodore.ca/gallery/magazines/misc/mos_605x_team_eetimes_august_1975.pdf> 

External links

General information:

• 6502.org - the 6502 microprocessor resource – Repository and portal (Mike Naberezny)
• 650x information – Concise description, photos of MOS and second source chips; at cpu-collection. de (Dirk Oppelt)
• a2DMAMagic – The secret, transparent, high-throughput 6502 DMA channel (by Jorge Chamorro Bieling)

Instruction set features:

• 6502 - the first RISC µP – With link to concise 6502 programming chart in PDF (Eric Clever)
• "The 6502 Gets Microprogrammable Instructions" – By Dennette A. Harrod, in BYTE, Volume 5, Number 10 (October 1980), pp. Byte magazine was an influential Microcomputer magazine in the late 1970s and throughout the 1980s because of its wide-ranging editorial coverage 282–5

Emulators and simulators:

• List of 6502 software emulators – At Zophar's Domain (Sam Michaels)
• 6502 simulator for Windows – At Dan Boris' homepage hosted by The Atari Gaming Headquarters
• Web-based 6502 compatible compiler and emulator written in JavaScript – by Stian Søreng

Early 6502 computers:

• Apple I Owners Club – Hosted by the Applefritter site (Tom Owad)
• KIM-1 schematics – At The Obsolete Technology Website (anonymous collector)

Hardware accelerators:

• 6502 accelerator information – At the Apple II History website (Steven Weyhrich)
• "Underneath the Hood of the SuperCPU" – By Jim Brain, in C=Hacking, Issue #12, Version 1. 3, March 1996 (search for "@(#)cmdcpu")

Hardware:

• The Western Design Center, Inc. (WDC) – home of the 65xx brand CMOS microprocessors.

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL. The Free On-line Dictionary of Computing ( FOLDOC) is an online searchable encyclopedic Dictionary of Computing subjects The GNU Free Documentation License ( GNU FDL or simply GFDL) is a Copyleft License for free documentation designed by the Free Software