MOS Technology 6502
The MOS Technology 6502 microprocessor, introduced in 1975, played a pivotal role in the early days of personal computing. Developed by a team led by Chuck Peddle, the 6502 was designed to be an affordable yet powerful alternative to existing processors like the Motorola 6800 and Intel 8080. This price advantage was achieved by using innovative design techniques and manufacturing processes, allowing the 6502 to be sold for just $25, compared to the $179-$360 price tag of its competitors. It quickly gained popularity and was the chosen CPU adopted by several home computer manufacturers, including Apple, Commodore, and Atari. Together with the Zilog Z80, it ignited a wave of projects that culminated in the personal computing revolution of the early 1980s.
A slightly modified version, the 6510, features a digital I/O port and a tri-state address bus. This enhanced version of the 6502 is the central processing unit (CPU) utilized in the Commodore 64. The inclusion of the digital I/O port and tri-state address bus allowed for more versatile interfacing with peripherals and memory.
Technical specifications and features[edit | edit source]
The 6502 CPU is an 8-bit microprocessor with a simple yet efficient design. Here are some key features:
- It has a 16-bit address bus, allowing it to address up to 64 KB of memory.
- Clock Speed: The 6502 operates at clock speeds ranging from 1 MHz to 3 MHz, depending on the specific implementation and application.
- Instruction Set: The 6502 has a relatively small and efficient instruction set, consisting of 56 instructions. This includes arithmetic operations, logical operations, data transfer instructions, and control instructions. The simplicity of the instruction set makes the 6502 easy to program.
- Registers: The 6502 has a small number of registers, including an 8-bit accumulator (A), two 8-bit index registers (X and Y), a stack pointer (SP), and a status register (P). This limited register set contributes to the simplicity and efficiency of the design.
- Addressing Modes: The 6502 supports multiple addressing modes, including immediate, zero page, absolute, indexed, indirect, and relative. These addressing modes provide flexibility in accessing memory and manipulating data.
Applications and legacy[edit | edit source]
The 6502 microprocessor found widespread use in a variety of applications, leaving a lasting legacy in the world of computing. Some notable applications include:
- Personal Computers: The 6502 was the heart of several iconic personal computers, including the Apple I and II, the Commodore PET and VIC-20, and the Atari 800.
- Video Game Consoles: The 6502 was used in several early video game consoles, including the Atari 2600 and the Nintendo Entertainment System (NES). Its ability to handle simple graphics and sound made it well-suited for gaming applications.
- Educational Tools: The 6502 was widely used in educational tools, such as the BBC Micro and the KIM-1. These devices helped introduce a generation of students to the world of programming and computer science.
- Embedded Systems: The 6502 found use in various embedded systems, including industrial controllers, automotive applications, and home appliances. Its simplicity and low cost made it a popular choice for these applications.
The legacy of the 6502 is evident in its influence on later microprocessors and its enduring popularity among enthusiasts and retro computing hobbyists. Although it is no longer being manufactured in its original form, its legacy lives on through its CMOS version, the WDC 65C02, developed by the Western Design Center. The 65C02 is still in production and widely used in embedded systems and educational tools. It is estimated that production volumes are in the hundreds of millions.
Links[edit | edit source]
|
Wikipedia: MOS_Technology_6502 |
