The BBC Master Compact was introduced in 1986. It was also named the Olivetti Prodest PC 128 S. The machine has a built-in 3.5" disk drive in addition to the other BBC Master features. Interestingly, the box houses only the disk-drive and the power supply unit, and the computer itself is housed in the keyboard. The two parts are connected by a large ribbon cable, making it vulnerable to cable breaks. The machine was mainly used in schools, and not very popular. It was quickly replaced when the Acorn 305 was introduced.

The BBC Master was produced in a few variations. Not all were produced in large quantities, and some of them are hard to find.

• Master 128 - First model of the Master series
• Master Turbo - Featured a 65C102 co-processor @4MHz
• Master AIV - Master Turbo with a SCSI interface and a Videodisc
• Master ET - For use on a network, only had RGB and Econet connectors
• Master 512 - Intel 80186 co-processor @ 10MHz to run DOS Plus and GEM
• Master Scientific - Prototype, NS32016 co-processor @ 8MHz
• Master Compact - Compact version of the 128

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.