BBC Micro
From Retrocomputing Wiki
| BBC Microcomputer | |
|---|---|
| Manufacturer | Acorn Computers |
| Type | Home computer |
| Released | December 1981 |
| Introductory price | £235 (Model A), £335 (Model B) |
| Discontinued | 1994 (Master series) |
| CPU | 6502A at 2 MHz |
| Memory | 16 KB (Model A), 32 KB (Model B) |
| Storage | Cassette, 5.25-inch floppy disk with DFS |
| Display | 8 screen modes up to 640 × 256; teletext Mode 7 |
| Sound | Texas Instruments SN76489, three voices plus noise |
| Operating system | Acorn MOS, BBC BASIC in ROM |
The BBC Microcomputer, usually called the BBC Micro or just the Beeb, is a series of 8-bit computers built by Acorn Computers for the British Broadcasting Corporation's Computer Literacy Project. It went on sale in December 1981. The BBC Micro was used in the great majority of British schools during the 1980s, and a whole generation of British programmers learned on it.
Contents |
[edit] Background
In 1980 the BBC planned a television series about computers and wanted a machine that viewers could buy and that would be featured in the programmes. Several British companies were considered, including Sinclair and Newbury Laboratories. Acorn, based in Cambridge, won the contract after Hermann Hauser and Chris Curry had their engineers build a working prototype in about a week for the BBC's visit.
The series, The Computer Programme, was first shown in January 1982, and was followed by several others. Demand was much higher than expected and early buyers had to wait months for their machines. The original prices of £235 for the Model A and £335 for the Model B were soon raised to £299 and £399.
[edit] Hardware
The BBC Micro was designed mainly by Steve Furber and Sophie Wilson. It uses a 6502 running at 2 MHz, which made it one of the fastest 8-bit home computers. The Model B has 32 KB of RAM, shared between programs and the screen.
The machine is well known for its many ports. Alongside the cassette, printer and RS-423 serial ports there is a user port, an analogue port for joysticks, a "1 MHz bus" for scientific equipment, and the Tube, which allowed a second processor to be connected. Second processors were sold with a faster 6502, a Z80 for running CP/M, and a 32016. Most machines in schools were also fitted with Econet, Acorn's low-cost network, so that a classroom could share a disk drive and a printer.
[edit] Screen modes
There are eight screen modes, numbered 0 to 7. The highest resolution is 640 × 256 in two colours (Mode 0), and Mode 2 gives 160 × 256 in 16 colours (eight of them flashing). Mode 7 uses a Mullard SAA5050 teletext chip to show colourful text and block graphics while using only 1 KB of memory, which is why so many BBC programs, from school software to the BBC's own Ceefax pages, look the way they do.
[edit] Software
BBC BASIC, written by Sophie Wilson, was one of the best BASICs of its time. It has procedures and functions with local variables, long variable names and a built-in 6502 assembler, so that assembly language could be mixed with BASIC in the same program.
The most famous BBC Micro game is Elite (1984), a 3D space trading game by David Braben and Ian Bell, published by Acornsoft. Other popular games include Repton, Chuckie Egg and Citadel.
[edit] Later models and legacy
Acorn released the cheaper Acorn Electron in 1983, the BBC Model B+ in 1985 and the BBC Master in 1986. About 1.5 million BBC Micros were sold in total.
Acorn's engineers went on to design their own processor, the Acorn RISC Machine or ARM, using BBC Micros with second processors to simulate it. The first ARM chips were tested in 1985 attached to a BBC Micro through the Tube.
