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Encyclopedia > MOS Technology 6502

The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle for MOS Technology in 1975. 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. 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 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. 8-bit refers to the number of bits used in the data bus of a computer. ... A microprocessor (sometimes abbreviated µP) is a programmable digital electronic component that incorporates the functions of a central processing unit (CPU) on a single semiconducting integrated circuit (IC). ... Electronics engineer Chuck Peddle is mostly known as the main designer of the MOS Technology 6502 microprocessor; the KIM-1 SBC; and its successor the Commodore PET school/business/home computer, both based on the 6502. ... MOS Technology, Inc. ... 1975 (MCMLXXV) was a common year starting on Wednesday. ... Die of an Intel 80486DX2 microprocessor (actual size: 12×6. ... Motorola (NYSE: MOT) is an American multinational communications company based in Schaumburg, Illinois, a Chicago suburb. ... Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is an American multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ... One of the first Z80 microprocessors manufactured; the date stamp says well before July 1976. ... Children playing on a Amstrad CPC 464 in the 1980s. ... 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 successful launch of a new bearing system for truck axles in 1919. ... Synertek was founded in 1973 as a masked ROM house that branched out into a fairly broad offering of MOS/LSI circuits (Static RAMs, ROMs, EPROMS, Dynamic and Static Shift Registers) and then sometime before 1979 became a second source to MOS Technologys 6502 microprocessor. ... A router, an example of an embedded system. ...

A MOS 6502 processor in a DIP-40 plastic package.
A MOS 6502 processor in a DIP-40 plastic package.

Contents

Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... ICs in DIP14-Package Several PDIPs and CERDIPS. The large CERDIP in the foreground is an 8080 processor. ...

History and use

The 6502 was designed primarily by the same engineering team that had designed the Motorola 6800. 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 sued immediately, and MOS agreed to stop producing the 6501 and went back to the drawing board. Motorola 6800 Microprocessor The 6800 is a microprocessor produced by Motorola and released shortly after the Intel 8080 in 1975. ... The 6501 is an eight-bit microprocessor, the first sold by MOS Technology. ... This article or section does not adequately cite its references or sources. ...


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. 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. Another roughly similar product was the Synertek SYM-1. Electronics engineer Chuck Peddle is mostly known as the main designer of the MOS Technology 6502 microprocessor; the KIM-1 SBC; and its successor the Commodore PET school/business/home computer, both based on the 6502. ... The KIM-1, short for Keyboard Input Monitor, was a small 6502-based microcomputer kit developed and produced by MOS Technology, Inc. ... The Rockwell AIM-65 computer was a trainer and development computer based on the MOS Technology 6502 microprocessor and introduced in 1976. ... Wikipedia does not have an article with this exact name. ...


The 6502 was introduced at $25 in September 1975, when the 6800 and Intel 8080 were selling for $179. 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. Far from the intended result, these price reductions actually legitimized the 6502[citation needed], which started selling by the hundreds. Intel C8080A processor. ...


One of the first "public" uses for the design was the Apple I computer, introduced in 1976. The 6502 was next used in the Apple II, and the Commodore PET. It was later used in the Atari home computers, the BBC Micro family, and a huge number of other designs now lost to history, such as Ohio Scientific. The 6510, a direct successor of the 6502 with a digital I/O port and a three-state bus, was the CPU utilized in the Commodore 64 home computer. (Commodore's disk drive, the 1541, had a processor of its own—it too was a 6502.) The Apple I was an early personal computer. ... The 1977 Apple II, complete with integrated keyboard, color graphics, sound, a plastic case and eight expansion slots. ... The PET (Personal Electronic Transactor) was a home-/personal computer produced by Commodore starting in the late 1970s. ... An Atari 800XL, one of the most popular machines in the series. ... The BBC Microcomputer System was a series of microcomputers and associated peripherals designed and built by Acorn Computers Ltd for the BBC Computer Literacy Project operated by the British Broadcasting Corporation. ... Ohio Scintific was a computer company that built and marketed computers from the late 1970s to the early 1980s. ... Image of the innards of a Commodore 64 showing the 6510 CPU (40-pin DIP, lower left). ... In digital circuits, a tri-state or three state buffer is used to allow multiple logic gates to drive the same output, usually a bus. ... Die of an Intel 80486DX2 microprocessor (actual size: 12×6. ... The Commodore 64 is the best-selling single personal computer model of all time. ... Front view of the most common version of the Commodore 1541 disk drive, with open disk slot. ...


Another important use of the 6500 family was in videogames. The first to make use was the Atari 2600 videogame console. The 2600 used an offshoot of the 6502 called the 6507, which had fewer pins and, as a result, could address only 8 KiB of memory. 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. Its North American and European equivalent, the Nintendo Entertainment System, also used the processor. The 6502 used in the NES was a modified version, 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. Called 2A03 in NTSC consoles and 2A07 in PAL consoles (the difference being the clock divider ratio and a lookup table for audio sample rates), this processor was produced exclusively for Nintendo. The Atari 2600, released in October 1977, was the first successful video game console to use plug-in cartridges instead of having one or more games built in. ... The Nintendo GameCube is an example of a popular video game console. ... The 6507 is an 8-bit microprocessor from MOS Technology, Inc. ... According to the International Electrotechnical Commission a kibibyte (a contraction of kilo binary byte) is a unit of information or computer storage. ... The Nintendo Entertainment System (North America, Europe, and Australia) NES redirects here. ... World map showing North America A satellite composite image of North America. ... This article is 150 kilobytes or more in size. ... NES redirects here. ... System-on-a-chip (SoC or SOC) is an idea of integrating all components of a computer system into a single chip. ... 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 sequence. ... In computer graphics, a sprite (also known by other names; see Synonyms below) is a two-dimensional image or animation that is integrated into a larger scene. ... Direct memory access (DMA) is a feature of modern computers, that allows certain hardware subsystems within the computer to access system memory for reading and/or writing independently of the central processing unit. ... The Ricoh 2A03 or RP2A03 was the 8-bit microprocessor in the Nintendo Family Computer and Nintendo Entertainment System video game consoles sold in Japan and North America. ... The references in this article would be clearer with a different and/or consistent style of citation, footnoting or external linking. ... The Ricoh 2A03 or RP2A03 was the 8-bit microprocessor in the Nintendo Family Computer and Nintendo Entertainment System video game consoles sold in Japan and North America. ... Television encoding systems by nation PAL, short for Phase Alternating Line, is a colour encoding system used in broadcast television systems in large parts of the world. ... Nintendo Company, Limited (任天堂 or ニンテンドー Nintendō; NASDAQ: NTDOY, TYO: 7974 usually referred to as simply Nintendo, or Big N ) is a multinational corporation founded on September 23, 1889[1] in Kyoto, Japan by Fusajiro Yamauchi to produce handmade hanafuda cards. ...


Description

The 6502 is an 8-bit processor with a 16-bit address bus. 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 was actually competitive with other CPUs using significantly faster clocks. 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 nevertheless used a PLA* for instruction decode and sequencing; and like most contemporary microprocessors, the chip does some overlapping of fetching and execution. 8-bit refers to the number of bits used in the data bus of a computer. ... An address bus is (part of) a computer bus, used by CPUs or DMA-capable units for communicating the physical addresses of computer memory elements/locations that the requesting unit wants to access (read/write). ... MegaHertz (MHz) is the name given to one million (106) Hertz, a measure of frequency. ... A programmable logic array (PLA) is a programmable device used to implement combinational logic circuits. ...


The low clock frequency moderated the speed requirement of memory and peripherals attached to the CPU as only about 50% of the clock cycle (this varied somewhat among chip versions) was available for memory access; 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)
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**. Inside was 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). The subroutine call/scratchpad stack's address space was hardwired to memory page $01, i.e. the address range $0100$01FF (256511). 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. Image File history File links MOS6502. ... Image File history File links MOS6502. ... ICs in DIP14-Package Several PDIPs and CERDIPS. The large CERDIP in the foreground is an 8080 processor. ... Motorola (NYSE: MOT) is an American multinational communications company based in Schaumburg, Illinois, a Chicago suburb. ... The 6800 is a microprocessor produced by Motorola and released shortly after the Intel 8080 in 1975. ... Intel C8080A processor. ... In computer architecture, a processor register is a small amount of very fast computer memory used to speed the execution of computer programs by providing quick access to commonly used values—typically, the values being in the midst of a calculation at a given point in time. ... In a computer CPU, an accumulator is a register in which intermediate arithmetic and logic results are stored. ... An index register in a computer CPU is a processor register used for modifying operand addresses during the run of a program, typically for doing vector/array operations. ... A status register is a collection of flag bits for a microprocessor that indicates the status of various mathematical operations. ... Simple representation of a stack In computer science, a stack is a temporary abstract data type and data structure based on the principle of Last In First Out (LIFO). ... The program counter (also called the instruction pointer in some computers) is a register in a computer processor which indicates where the computer is in its instruction sequence. ...


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. 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, a concept from computer science, are an aspect of the instruction set architecture in most central processing unit (CPU) designs. ... The zero page is the memory address page at the absolute beginning of a computers address space (the lowermost page, covered by the memory address range 0 . ... A PDP-8 on display at the Smithsonians National Museum of American History in Washington, D.C.. This example is from the first generation of PDP-8s, built with discrete transistors and later known as the Straight 8. ...


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). 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. Immediate mode used an 8-bit literal operand. Addressing modes, a concept from computer science, are an aspect of the instruction set architecture in most central processing unit (CPU) designs. ... In mathematics, an operand is one of the inputs (arguments) of an operator. ... Look up literal, literally in Wiktionary, the free dictionary. ...


The indirect modes were useful for array processing and other looping. 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; incrementing Y in order to walk the array (byte wise) took only two additional cycles. The Y register was thus an index register in a true sense, and the 6502's specifications, saying 8-bit index registers***, may be taken literally; it is about 8-bit indexing, not 8-bit addressing. 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. This article or section does not cite its references or sources. ...


See the Hello world! article for a simple but characteristic example of 6502 assembly language. An assembly language is a low-level language used in the writing of computer programs. ...


* Which required about 15% of the chip area.


** The 6800 was designed around 1973 at a time when (small bipolar) memories were relatively fast. It therefore made sense to use RAM instead of wasting expensive NMOS chip area on CPU-registers (then a significant part of the CPU) The 6800 is a microprocessor produced by Motorola and released shortly after the Intel 8080 in 1975. ... Die of an Intel 80486DX2 microprocessor (actual size: 12×6. ...


*** This is where the 6502 differs most from the Motorola 6800, which has one 16-bit address/index register instead of two eight-bit index registers. Motorola 6800 Microprocessor The 6800 is a microprocessor produced by Motorola and released shortly after the Intel 8080 in 1975. ...


Detailed behaviour

  • The processor's NMI input is edge-sensitive, which means that if the source of an NMI holds the line low NMI's are effectively disabled.
  • 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.

The acronym NMI has several meanings: New Media Inc - GMA Networks Iteractive company. ... The acronym NMI has several meanings: New Media Inc - GMA Networks Iteractive company. ... The acronym NMI has several meanings: New Media Inc - GMA Networks Iteractive company. ... A Non-Maskable Interrupt (NMI) is a special type of interrupt that can not be ignored by standard interrupt masking techniques. ... In computing, an interrupt request (or IRQ) is a phrase used to refer to either the act of interrupting the bus lines used to signal an interrupt, or the interrupt input lines on a Programmable Interrupt Controller (PIC). ... Look up assertion in Wiktionary, the free dictionary. ...

Dubious features

  • The 6502 and NMOS derivatives are noted for having a variety of undocumented instructions, which vary from one chip manufacturer to the next. 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. 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). There was a company called Eastern House Software who developed a device called "Trap65" that plugged between the processor and its socket to convert (trap) unimplemented opcodes into BRK (software interrupt) instructions. 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. All of the undefined opcodes were replaced by NOP instructions in the 65C02 CMOS version (although with varying byte sizes and execution times).
  • The 6502's memory indirect jump instruction, JMP (<address low-word>), was partially broken. If <address low-word> was hex xxFF (i.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.
  • A method to mask the NMI is not to return from the Interrupt the first time it is used.
  • The N (result negative), V (sign bit overflow) and Z (result is zero) status flags may be invalid after performing arithmetic operation while processor is in BCD mode. Only the C (carry) flag is always valid. It was also fixed in the CMOS derivatives, therefore this feature may be used to cleanly distinghish 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. It should be noted that the popular Commodore 64's kernel did not correctly handle this type of situation, requiring that IRQs be disabled during BCD math operations. 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). BRK is most often used to interrupt program execution and start a machine language monitor for testing and debugging during software development. It could also be used to route program execution using a simple jump table (analogous the way the 8088 and derivatives handle software interrupts by number). 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. This fault was corrected in the CMOS implementation of the processor.
  • The JSR (call) instruction pushed 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 pulled the return address off the stack and added one to it before placing it into the program counter, resulting in automatic compensation for this design quirk. 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.

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 CPUs designer or manufacturer, which nevertheless has an effect. ... A programmable logic array (PLA) is a programmable device used to implement combinational logic circuits. ... Microprocessors perform operations using binary bits (on/off/1or0). ... 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. ... NOP or NOOP (short for No OPeration) is an assembly language instruction, sequence of programming language statements, or computer protocol command that does nothing at all. ... WDC 65C02 Microprocessor // Introduction The W65C02S is a low power, cost effective 8-bit microprocessor. ... Static CMOS Inverter Complementary-symmetry/metal-oxide semiconductor (CMOS) (see-moss, IPA:), is a major class of integrated circuits. ... An indirect branch (also known as a computed jump, indirect jump and register-indirect jump) is a type of program control instruction present in some machine language instruction sets. ... In mathematics and computer science, hexadecimal, base-16, or simply hex, is a numeral system with a radix, or base, of 16, usually written using the symbols 0–9 and A–F, or a–f. ... Static CMOS Inverter Complementary-symmetry/metal-oxide semiconductor (CMOS) (see-moss, IPA:), is a major class of integrated circuits. ... The acronym NMI has several meanings: New Media Inc - GMA Networks Iteractive company. ... In computing, an interrupt is an asynchronous signal from hardware or software indicating the need for attention. ... A status register is a collection of flag bits for a microprocessor that indicates the status of various mathematical operations. ... 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 sequence. ... Static CMOS Inverter Complementary-symmetry/metal-oxide semiconductor (CMOS) (see-moss, IPA:), is a major class of integrated circuits. ... The Commodore 64 is the best-selling single personal computer model of all time. ... A kernel connects the application software to the hardware of a computer. ... In computer science, an interrupt is a signal from a device which typically results in a (register) context switch: that is, the processor sets aside what its doing and does something else. ... This is a disambiguation page &#8212; a navigational aid which lists other pages that might otherwise share the same title. ... In 6502 assembly language programming, BRK is an opcode that causes a software interrupt or trap. ... In computer science, an interrupt is a signal from a device which typically results in a (register) context switch: that is, the processor sets aside what its doing and does something else. ... The 6800 is a microprocessor produced by Motorola and released shortly after the Intel 8080 in 1975. ... 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 and change memory locations on the machine, with options to load and save memory contents from/to secondary storage. ... The Intel 8088 is an Intel microprocessor based on the 8086, with 16-bit registers and an 8-bit external data bus. ... In computer engineering, an interrupt is a signal from a device which typically results in a context switch: that is, the processor sets aside what its doing and does something else. ... 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. ... Look up Stack in Wiktionary, the free dictionary. ... The program counter (also called the instruction pointer in some computers) is a register in a computer processor which indicates where the computer is in its instruction sequence. ...

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 KiB 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. 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. If you were looking for the Western Digital Corporation, see Western Digital. ... The W65816 (also: 65C816), a 16-bit microprocessor developed by the Western Design Center (WDC), is an expanded and compatible successor to the venerable MOS Technology 6502. ... The W65816 (also: 65C816), a 16-bit microprocessor developed by the Western Design Center (WDC), is an expanded and compatible successor to the venerable MOS Technology 6502. ... In a computer CPU, an accumulator is a register in which intermediate arithmetic and logic results are stored. ... An index register in a computer CPU is a processor register used for modifying operand addresses during the run of a program, typically for doing vector/array operations. ... An electronic component is a basic electronic building block packaged in a discrete form with two or more connecting leads or metallic pads. ... The integrated circuit from an Intel 8742, an 8-bit microcontroller that includes a CPU running at 12 MHz, 128 bytes of RAM, 2048 bytes of EPROM, and I/O in the same 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. Mitsubishi Logo The Mitsubishi Group ), Mitsubishi Group of Companies, or Mitsubishi Companies, all refer to a large grouping of independently operated Japanese companies which share the Mitsubishi brand name. ... Renesas Technology Corporation ) is a Japanese semiconductor manufacturer. ...


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 was founded in 1973 as a masked ROM house that branched out into a fairly broad offering of MOS/LSI circuits (Static RAMs, ROMs, EPROMS, Dynamic and Static Shift Registers) and then sometime before 1979 became a second source to MOS Technologys 6502 microprocessor. ...


32-bit derivatives

The Western Design Center is developing the W65T32 Terbium, a compatible 32-bit follow-up to the W65C816. The Terbium is named after the 65th element as 65 is the prefix to all of WDC's microprocessor number identifiers. The chip has 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. Zip Technology's patent #4,794,523 eventually forced Bits and Pieces to cease manufacturing of the Rocket Chip.

The 65C02 Microprocessor is a slightly upgraded version of the popular and venerable 6502 microprocessor. ... W65C816S microprocessor in a DIP40 package. ... MegaHertz (MHz) is the name given to one million (106) Hertz, a measure of frequency. ... This article is about the computer term. ...

6502 trivia

  • 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."
  • A Byte magazine article once referred to the 6502 as "the original RISC processor," due to its efficient, simple, and nearly orthogonal instruction set (most instructions work with most addressing modes), as well as its 256 zero-page "registers". It is technically not a RISC design, however, as operations can read any memory cell (e.g ADC) and some even modify memory (e.g. INC), contrary to the basic load/store philosophy of RISC. Furthermore, orthogonality is also equally often associated with CISC processors.

The Terminator (also known as Terminator in some early trailers and posters) is a 1984 science fiction/action film featuring former bodybuilder Arnold Schwarzenegger in what would become his best-known role, and also starred Linda Hamilton and Michael Biehn. ... Arnold Alois Schwarzenegger (German pronunciation (IPA): ) (born on July 30, 1947) is an Austrian-American bodybuilder, actor and an American politician, currently serving as the 38th Governor of California. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... This article needs cleanup. ... The 1977 Apple II, complete with integrated keyboard, color graphics, sound, a plastic case and eight expansion slots. ... A checksum is a form of redundancy check, a very simple measure for protecting the integrity of data by detecting errors in data that is sent through space (telecommunications) or time (storage). ... Nibble was a magazine for Apple II users, with a focus on programming. ... Bender Bending Rodríguez, more commonly known as Bender (assembled c. ... Futurama is an Emmy Award-winning American animated sitcom created by Matt Groening (creator of The Simpsons) and David X. Cohen for the Fox Network. ... Fry and the Slurm Factory is episode 13 in season 1 of Futurama. ... The University of Tasmania (also abbreviated as UTAS, UTas or Tas Uni) is a well-regarded Australian university, with three campuses in Tasmania. ... A Fachhochschule (plural: Fachhochschulen) or University of Applied Sciences in Austria, Germany, Liechtenstein and Switzerland is something like a polytechnic. ... For other uses, see Cologne (disambiguation). ... The University of Exeter is a leading red brick university. ... “Devonshire” redirects here. ... Skinner Memorial Chapel, Carleton College Carleton College is an independent, non-sectarian, coeducational, liberal arts college in Northfield, Minnesota, USA. The school was founded on November 14, 1866, by the Minnesota Conference of Congregational Churches as Northfield College. ... The University of Hull, also known as Hull University, is an English university in East Yorkshire which was founded in 1927. ... Country Italy Region Lombardy Province Brescia (BS) Mayor Paolo Corsini (since June 10, 2003) Elevation 150 m Area 90 km² Population  - Total (as of December 31, 2004) 192,165  - Density 2,087/km² Time zone CET, UTC+1 Coordinates Gentilic Bresciani Dialing code 030 Postal code 25100 Frazioni Fornaci, Sant... Universidad APEC (UNAPEC) is a university in Santo Domingo, Dominican Republic. ... Santo Domingo de Guzmán, population 2,061,200 (Metro) (2003), estimated 2,253,437 (Metro) in 2006, is the capital and the largest city of the Dominican Republic. ... December 1975 issue of Byte (Vol 1. ... Reduced Instruction Set Computer (RISC), is a microprocessor CPU design philosophy that favors a smaller and simpler set of instructions that all take about the same amount of time to execute. ... Orthogonal instruction set is a term used in computer science. ... This article is about the computer architecture. ... Orthogonal instruction set is a term used in computer science. ... A Complex Instruction Set Computer (CISC) is an instruction set architecture (ISA) in which each instruction can indicate several low-level operations, such as a load from memory, an arithmetic operation, and a memory store, all in a single instruction. ...

See also

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6502 Assembly

Image File history File links Wikibooks-logo-en. ... Wikibooks logo Wikibooks, previously called Wikimedia Free Textbook Project and Wikimedia-Textbooks, is a wiki for the creation of books. ... The Lisa assembler (Lazerwares Interactive Symbolic Assembler), written by Randall Hyde (Randy Hyde) in the late 1970s, is an interactive MOS 6502 assembler for Apple II computers. ... This is a list of home and office computers by category where the main category is the home computers CPU wordlength (8/16/32/64 bits) and the subcategory is the specific CPU used in each machine. ...

References

  • Bagnall, Brian (2005). On the Edge: The Spectacular Rise and Fall of Commodore. Variant Press. ISBN 0-9738649-0-7.
  • 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). 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.

Rodnay Zaks (born in Paris, France) is a prolific author of books on computer programming[1], including the seminal Programming the Z80 and Programming the 6502. ...

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)

Instruction set features:

Emulators and simulators: Portable Document Format (PDF), sometimes mistaken for Printable Document Format, is an open file format created by Adobe Systems in 1993 and is now being prepared for submission as an ISO standard[1]. It is used for representing two-dimensional documents in a device independent and resolution independent fixed-layout... December 1975 issue of Byte (Vol 1. ...

  • 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

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:


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. ... GNU logo (similar in appearance to a gnu) The GNU Free Documentation License (GNU FDL or simply GFDL) is a copyleft license for free content, designed by the Free Software Foundation (FSF) for the GNU project. ...



65xx-series CPUs from MOS Technology, second source/clone vendors, and the Western Design Center

MOS 4510MOS 6501MOS 6502WDC 65C02Hudson HuC6280Ricoh 2A03MOS 6507MOS 6508MOS 6509
MOS 6510 (and 7501, 8500, 8501) ● MOS 8502MOS 65CE02WDC 65802WDC 65816Ricoh 5A22 ● Nintendo SA-1 Image File history File links MOS_Technology. ... Image File history File links WDClogo_small. ... MOS Technology 65xx is a family of 8-bit microprocessors from MOS Technology, based on the Motorola 6800 (introduced ca. ... Die of an Intel 80486DX2 microprocessor (actual size: 12×6. ... MOS Technology, Inc. ... If you were looking for the Western Digital Corporation, see Western Digital. ... The MOS Technology 4510 was the MOS-manufactured microcomputer chip used in the (unreleased) Commodore 65 8-bit home/personal computer. ... The 6501 is an eight-bit microprocessor, the first sold by MOS Technology. ... WDC 65C02 Microprocessor // Introduction The W65C02S is a low power, cost effective 8-bit microprocessor. ... The HuC6280 8-bit microprocessor is Japanese company Hudson Softs improved version of the WDC 65C02 CPU. The most notable product using the HuC6280 is NECs TurboGrafx 16 video game console. ... The Ricoh 2A03 or RP2A03 was the 8-bit microprocessor in the Nintendo Family Computer and Nintendo Entertainment System video game consoles sold in Japan and North America. ... The 6507 is an 8-bit microprocessor from MOS Technology, Inc. ... The MOS Technology 6508 was an 8-bit microprocessor designed by MOS Technology. ... The MOS Technology 6509, an enhanced version of the popular 6502 microprocessor, was capable of addressing up to 1 megabyte of RAM via bank switching. ... Image of the innards of a Commodore 64 showing the 6510 CPU (40-pin DIP, lower left). ... The MOS Technology 8502 was MOSs microprocessor used as one of the two¹ CPUs in the Commodore 128 home/personal computer. ... The 65CE02 (a derivative of 6502/65c02) is a CPU core developed by Commodore Semiconductor Group (formerly known as Commodore MOS) that has been used in the CSG 4510 micro controller (that combined a CPU and several I/O components) in the Commodore C64DX/C65. ... W65C816S microprocessor in a DIP40 package. ... W65C816S microprocessor in a DIP40 package. ... The Ricoh 5A22 is the microprocessor CPU produced by Ricoh for the Super Nintendo Entertainment System (SNES) video game console. ... The Nintendo SA-1 is a microprocessor developed by Nintendo for use in Super Nintendo Entertainment System (SNES) game cartridges. ...


 
 

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