The Atari 2600 Jr. was launched in 1986 to reduce cost of the system. The case resembled that of the Atari 7800 and the system was advertised as a budget gaming system, and retailed under $49.99. Some new games were developed for the system, but the architecture was the same as the Atari 2600 and could not really compete with the systems that were available on the market.

The MOS Technology 6507 CPU is an 8-bit microprocessor based on the 6502 technology. Basically it is a 6502 packaged in a 28-pin DIP instead of a 40-pin. This made the chip cheaper to package and integrate in systems. MOS technology achieved this by reducing the address bus from 16 bits to 13 bits and removing a number of other pins used only for certain applications.

The 6507 is the main chip of the Atari-2600 family of consoles. The Chip was launched in 1975 and could, due to the reduced number of address pins, address 8KByte of memory. This proved to be enough for the Atari consoles and for peripherals such as the 850 Serial & Parallel Interface, the 1050 disk drives and more.

The 6502 is an 8-bit MicroProcessor designed by MOS Technology. The team was led by Chuck Peddle and had also worked on the Motorola 6800. The 6502 is a simplified, but faster and cheaper design than the 6800.

The 6502 was introduced in 1975 and was the cheapest microprocessor on the market. Together with the Zilog Z80, the 6502 helped start the home computer revolution of the 1980s. The 6502 was used in a wide range of devices: the Atari 2600, the 8-bit Atari home computers, the Apple II, the Nintendo Entertainment System, the Commodore 64, the BBC Micro and many others. All used the 6502 or a variation of it.

The 6502 is a 1MHz design, while the 6502A is designed for 2MHz. The 6502A is 100% compatible with the original 6502.

Commodore soon bought MOS Technology, but conitnued to sell the microprocessor to competitors and licensed the design to other manufacturers.