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BBC Micro

1981–1994 · desktop

Specifications

Cpu: MOS Technology 6502A, 2 MHz
Ram: max: 32 KB directly addressable; paged ROM/sideways RAM expansions could add banked memory for extra software, not general-purpose RAM · base: 32 KB (Model B); the cheaper Model A shipped with 16 KB
Ports: Composite video · RGB (analogue) video · UHF/RF TV output · Cassette port · 1 MHz bus (disc interface, expansion) · Tube interface (second processor) · Econet network port · RS-423 serial · Analogue joystick port · User port (8-bit parallel I/O) · Printer (Centronics) port
Display: Six text/graphics MODEs via on-board video hardware, up to 640x256 in 2 colors or 320x256 in 4 colors; composite, RGB, and UHF/RF output
Storage: base: Cassette tape via the built-in cassette port (no internal storage) · options: Acorn 5.25" floppy disc drive via the Disc Filing System (DFS) interface, single or double density
Os Support: latest: BBC BASIC II / MOS in ROM; later boards shipped BASIC IV and MOS updates, GEOS-style alternatives never applied here · shipped: BBC BASIC II with the MOS operating system, both in ROM
Release Price: £335

Variants

Models

Model ACut-down launch variant with 16 KB RAM and fewer ports populated; most were upgraded to Model B spec.

Model B+1985 update with 64 KB RAM (32 KB shadow RAM) and, on the B+128, 128 KB.

Upgrade paths

RAM

Model A to Model B spec (16 KB to 32 KB) via an official Acorn upgrade kit; third-party sideways RAM boards added banked ROM-replacement memory · The 6502's 64 KB address space is largely consumed by I/O and the paged ROM area, which is why later expansion went sideways (banked) rather than adding linear RAM.

~£70 for the official Acorn RAM/upgrade kit at the time

MODERATE

storage

Dual 5.25" floppy drives via the DFS/1 MHz bus interface · The disc interface was an optional board fitted inside the case on early units, standard on later ones.

~£200-£300 for a drive and DFS kit at the time

MODERATE