Acorn Proton (BBC Model A) BBC Model B and Plus

BBC Model B

Acorn launched the Proton (later called as BBC) on December 1981, after BBC had chosen the machine for its TV program. Although it was launched in December 1981, It was available for the public in summer of 1982. In the 80’s the Proton was everyone’s dream. Acorn to satisfy these users released another type of computer similar to the Proton, code named the Electron.

The outer design of the machine is not very impressive, but the specifications for that time, were outstanding. Acorn released four different version of the machine, The Proton (BBC Model A) BBC Model B, BBC Plus, and BBC 128K. The only problem that you could encounter with the BBC Model A and B, is the limited amount of RAM while programming. The machine has various ports and connections. One of the most connection used was the floppy drive, a standard Shugart 34-pin connection drive. Another interesting port is the analogue port for joystick, mice and touch table. The ECONET was used to connect the machine on a network. This particular port was only installed on request and it was very expensive. There is another port to upgrade the CPU from a 6502 to a Z80 processor. This upgrade was mainly used to use CP/M OS and to run Z80 based software from third party companies. Today the BBC is still considered one of the best system ever produced in the 80’s and a very requested machine among computer collectors.

BBC (Proton)
Approx £399 in  1982
01-ANB53-5507357, 08-ANB01-3019475
6502A 8-bit CPU running at a frequency of 2 Mhz.
32 Kbytes of Rom. The machine has also the facility to include more Rom packages inside. 32Kbytes Ram expandable to 64Kbytes (Model B was released with 64Kb).
Medium creamy plastic case with black keys and red function keys. The keyboard is slightly a non standard QWERTY style with 12 function keys, caps, caps lock and four arrow keys. The function keys are all programmable and a reference card of the keys can be inserted under the plastic holder on top of the keyboard.
The BBC has 8 display modes: Mode 0: 640×256 2 colours Text: 80×32, Mode 1: 320×256 4 colours Text: 40×32, Mode 2: 160×256 16 colours Text: 20×32, Mode 3: Text: 80×25 2 colours, Mode 4: 320×256 2 colours Text: 40×32, Mode 5: 160×256 4 colours Text: 20×32, Mode 6: Text: 40×25 2 colours, Mode 7: Teletext mode 40×25. The colours are all selectable from a palette of 8 colours, both normal or flashing mode.
The BBC is equipped with an SN76489 sound chip, capable of producing 3 channels of sound and an extra channel of white noise. The sound is produced on an internal small speaker.
1 x BBC High Speed Bus,
1 x Tube expansion,
1 x User Port,
1 x Floppy Port,
1 x Parallel printer port,
1 x Analogue port,
1 x ECONET Port,
1 x Tape Recorder 1200 bps,
1 x RF TV output,
1 x Composite Video out,
1 x RGB Monitor connector,
1 x RS-423 serial port.
Internal Power supply with +12v, +5v, -12v supply.
409mm x 358mm x 78mm
More than 60,000 units sold in the UK and some in Europe.

The club currently owns 15 Acorn BBC in fully working condition.One of the machine is boxed and complete, but the others are loose. We have several manuals from the loose ones, and a good collection of software. As for peripherals we have several different drives and accessories in the collection. Locally the BBC was very popular and mainly was used in private schools. The Main agent for the BBC was Sirap Computers, which he donated all his ex old stock to us including CUB and Philips Monochrome monitors, and other peripherals.


Analogue Port

15-Pin D-Sub Female

Pin Name Dir Desc
1 VCC OUT +5V 500ma supply
2 GND N/A Ground
3 GND N/A Ground
4 AINCH3 IN Analogue IN Channel3
5 AGND N/A Analogue Ground
6 GND N/A Ground
7 ACH1 IN Analogue IN Channel1
8 AGND N/A Analogue Ground
10 FIRE1 IN Fire Btn 1
11 VREF IN Vertical Reference
12 AINCH2 IN Analogue IN Channel 2
13 FIRE0 IN Fire Btn 2
14 VREF OUT Vertical Reference
15 AINCH0 IN Analogue IN Channel 0


Cassette Port

Din 7 Pin 360

Pin Name Dir Desc
2 GND N/A Ground
3 AIN IN Audio IN
5 N/C N/A No Conection
6 MSW IN Motor Switch
7 MSW OUT Motor Switch



5 Pin Din 180

Pin Name Dir Desc
2 GND N/A Ground
3 CLK OUT Clock
5 CLK OUT Clock


RGB Monitor

6 Pin DIN (DIN45322) Female at the Computer

Pin Name Dir Desc
1 ARED OUT Analogue Red
2 AGRN OUT Analogue Green
3 ABLU OUT Analogue Blue
4 CSYN OUT Comp Sync
5 GND N/A Ground
6 VCC OUT +5V 500ma Supply



5 Pin Din Female at the computer

Pin Name Dir Desc
1 TxR IN Data In
2 TxS OUT Data Out
3 CTS IN Clear to send
4 RTS IN Ready to send
5 GND N/A Ground