Home Forums Blogs Articles Photos Videos Contact FAQ

BBC Micro - Specifications

BBC Micro - Specifications: Encyclopedia II - BBC Micro - Specifications

Four independent sound channels (one noise and 3 melodic) using the Texas Instruments SN76489 sound chip Built-in hardware support included: pluggable ROMs, directly or via "Sideways" daughterboard tape interface (with motor control), using a variation of the Kansas City standard data encoding scheme Centronics parallel printer (model B only) serial communication (using RS-423, a superset of RS-232) display output for TV, RGB or 1v p-p video monitor four analo ...

BBC Micro: Encyclopedia II - BBC Micro - Specifications

BBC Micro - Specifications

2 MHz MOS Technology 6502A processor (6512A in model B+)
32 KB ROM (16 KB MOS (Machine Operating System), 16 KB read-only paged space defaulting to the BBC BASIC EPROM)
32 KB RAM (16 KB in model A, 64 KB in model B+)
Full-travel keyboard with a top row of ten red-orange function keys f₀ − f₉
Highly configurable graphics display based on the Motorola 6845. Eight graphics modes were provided by the system ROM:
- Modes 0 to 6 could display a choice of colours from a palette of sixteen; the eight basic RGB colours (black, red, green, yellow, blue, magenta, cyan, white) and said colours in a flashing state;
- Mode 7's Teletext capability was provided by a Mullard SAA5050 Teletext chip

Graphics mode	Resolution (X×Y)		Colours	Video RAM used (KB)
Graphics mode	Char cells	Pixels	Colours	Video RAM used (KB)
0	80 × 32	640 × 256	2	20
1	40 × 32	320 × 256	4	20
2	20 × 32	160 × 256	16	20
3	80 × 25	–	2	16
4	40 × 32	320 × 256	2	10
5	20 × 32	160 × 256	4	10
6	40 × 25	–	2	8
7	40 × 25	Teletext	8	1

Four independent sound channels (one noise and 3 melodic) using the Texas Instruments SN76489 sound chip
Built-in hardware support included:
- pluggable ROMs, directly or via "Sideways" daughterboard
- tape interface (with motor control), using a variation of the Kansas City standard data encoding scheme
- Centronics parallel printer (model B only)
- serial communication (using RS-423, a superset of RS-232)
- display output for TV, RGB or 1v p-p video monitor
- four analogue inputs (suitable for two joysticks)
- proprietary "Tube" interface for external second CPU (options included a 3 MHz extra 6502, a Zilog Z80 for e.g. CP/M, an NS32016, an ARM1, and others)
- a "user port" (model B only), and
- generic expansion through the "1 MHz bus".
Use of floppy disk drives required the installation of a DFS ROM (disk filing system) and a disk controller card based on the 8271 chip (later, and on the model B+, the WD1770)
Via "The Tube" a second CPU could be attached (including a 3 MHz extra 6502, a Zilog Z80 for e.g. CP/M, an NS32016, an ARM1, and others)

The default Model A/B motherboard could also be upgraded by adding the following components:
- "Econet" large-scale low-cost networking system
- ROM/RAM cartridge filing system via a slot to the left of the keyboard
- speech synthesis hardware (Very few people bothered with this upgrade - the synthesiser was rather limited, and some games programmers succeeded in producing more versatile software speech synthesis using only the standard sound hardware)
- Reset Button (It is doubtful if anyone ever added this, as a complete hardware reset can be accomplished by keyboard shortcuts at any time, even if the machine has crashed.)

The case was designed by industrial designer Allen Boothroyd of Cambridge Product Design Ltd. (Note that the photograph in this article is not coloured correctly - the machine was actually produced in a warm yellow/cream colour, as opposed to the sterile beige boxes favoured by other manufacturers. Somewhat amusingly, this also means collectors of BBC computers do not need to worry as much about the dreaded "yellowing" that plagues the aging plastic housings of many other machines.)