Acorn BBC Micro

Vital Statistics

Introduced December 1981
Retired: 1 Sep 1984 (Model A), 1987 (Model B)
Price: £235 (Model A), £335 (Model B), £499 (Model B+)
Quantity Sold: unknown (>1,000,000)
Countries: UK and Europe
Dimensions: 410 x 345 x 65 mm
Weight: 3.7kg
Ports: RF out, BNC, RGB video, RS423, cassette, user port, printer port, "Econet", disk drive (Model B onwards)
CPU: MOS 6502 @ 2 MHz
Usable RAM: 16K (Model A), 32K (Model B), 64K or 128K (Model B+), 128K (Master)
Built-in ROM: 32K (Models A/B), 48K (Model B+), 128K (Master)
Colours: 8 colours (+ 8 flashing equivalents)
Graphics: 640 x 256 (2-colour), 320x256 (4-colour), 160x256 (16-colour) or text resolution of 80x32
Sound: 3 main channels + 1 noise
Built-in Language: BBC BASIC
Clones: SCL Unicorn
Codenames: Proton

More ...

What's it like today?

Fun Factor: 4/5
Geek Factor:
Model/Rarity/Price (Poor - BNIB/Mint):
BBC Model A £75-£200
BBC Model B £25-£100
BBC Model B+ £120-£200
BBC Master 128 £40-£120
BBC Master Compact £45-£180


When Acorn introduced the BBC Micro, it radically changed the personal computer market. Pitched at schools across the UK as the computer of choice for education, it led the way for many young people to learn about the power and usefulness of computing. The name 'BBC' was used because of the involvement the British Broadcasting Corporation had in promoting the computer.

It all began when the BBC started the "Computer Literacy Project" back in early 1981 following a highly influential television series from the ITV called "The Mighty Micro". The BBC commissioned all the major personal computer manufacturers of the time to create a brand new usable home computer for the mass market with the intention of demonstrating a variety of computer uses on its own television series called "The Computer Programme". The eventual contract was won by Acorn Computer, who already had the basics of a new machine to succeed their Atom computer. This new computer had been called the "Proton" during its development, but was renamed for release as the "BBC Microcomputer". The first unit to be produced was the Model A which came with 16K of RAM. At its heart was the MOS Technology 6502 microprocessor running at 2 MHz.

The Model B followed in 1982 with 32K RAM, expandable to 64K. It came as standard with new expansion ports missing on the former Model A, including a RS-423 serial port, parallel port, 'User' port, an analogue interface, direct access to the 1 MHz bus, and the 'Tube' interface (mostly used for adding a second CPU). You could upgrade a Model A to be a Model B with little effort if you only wanted to expand the memory. This involved adding the new user/printer 6522 VIA (Versatile Interface Adapter) chip, the new memory chips and break a link on the circuit board. Optional extras for both the Model A and Model B were a disk interface, Econet interface, and a speech system.

In mid-1985, the B was replaced by the Model B+, with a choice of either 64K RAM or 128K RAM as standard and built-in support for Econet and external disk drives (both of which were available as upgrades for the Model A and B). The extra 32K of RAM (for the 64K model) was split between 20K for shadow video memory, and 12K for workspace (BASIC). The Model B+ retained the same casing design as the previous Models A and B. There were, however, some incompatibilities of the new system with the original Model A and B such as the replacement of the old Western Digital 1770 floppy disk controller chip to the more advanced Intel 8271 controller, as the two were very different. The Model B+ also made use of the newer MOS 65C12 microprocessor, replacing the MOS 65C02 in the Models A and B.


The B+ was superceded very quickly by the BBC Master range in 1986 - initially a 128K machine, this series was to be the last of the 8-bit Acorns. The Master came with spreadsheet and word processing ROMs built-in and two cartridge slots, as well as ADFS (the Advanced Disk Filing System) fitted as standard.

After the launch of the BBC Master 128 (see left), then came the Master 512 and finally the Master Compact (see right picture) which employed a different case design with the power supply separated from the keyboard into its own box that sat under the monitor. This also contained the floppy disk drive(s).

The Master series came with such features as shadow RAM (for off-screen buffered video), external EPROM cartridge slots, support for an internal co-processor card (for the 65C02 co-processor) and even space to fit a SCSI controller, useful for the Master AIV which was apparently the world’s first multimedia machine (Google "Domesday"), using a Philips SCSI laserdisc player.

In total, seven distinct Master machines were manufactured, each one pitched at a different price point and end use:

Master 128 - original machine with 128K RAM and 128K ROM.
Master Turbo - as 128 but fitted with a 65C102 coprocessor card
Master AIV - as Turbo but fitted with a SCSI interface and the Video Filing System (VFS) ROM - used for the Domesday Project
Master ET ("Econet Terminal") - cut-down version of Master 128 with only the Econet, RGB and Composite video ports.
Master 512 - as Master 128 but fitted with the Intel 80186 coprocessor card complete with 512K RAM. With this coprocessor, it could run DOS+ and the GEM graphical user interface.
Master Scientific - Never released - It was to originally contain the 32016 coprocessor card with 32081 floating point maths coprocessor and 512K RAM. It would also run the 'PANOS' operating system with this coprocessor card.
Master Compact - Physical casing changed to a 'split' design. This meant that only the ADFS ROM was supplied as standard (no Word Processor or Spreadsheet ROMs). It had no real-time clock fitted, as it was expected this could be fetched over Econet. The under-monitor case contained the 3.5" floppy disk drive and the system's power supply.

By 1986, Acorn had already sold part of its business to Olivetti following dire financial problems with the Electron and other projects that weren't ready for sale. Offsetting this was that the Master was selling very well, mostly to schools and universities, just as with the original Acorn BBC. All the while, Acorn was close to finalising their next series of computers, the Acorn Archimedes. The "Acorn RISC Machine Project", which was started way back in October 1983 was based on Acorn's own in-house architecture, which made use of RISC (Reduced Instruction Set Computing), and was launched in June 1987 with the A300 and A400 models. The BBC series dwindled into history following the Archimedes launch, as home consumers moved to Commodore Amiga and Atari ST 16-bit computers, and the Education sector upgraded to the Archimedes.


This page was last updated on 28th June 2019.