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BBC Master

1986–1994 · desktop

Specifications

Cpu: MOS Technology 65C12 (CMOS 6502 variant), 2 MHz; optional 65C102 or Z80 second processor on the Master 512 / Turbo boards
Ram: max: 128 KB on-board; the Master 512 add-on card brought a further 512 KB for its 80186 co-processor, used only by that subsystem · base: 128 KB (64 KB main RAM plus 64 KB shadow/sideways RAM)
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: Same video ULA as the BBC Micro, up to 640x256 in 2 colors or 320x256 in 4 colors; composite, RGB, and UHF/RF output; Teletext MODE 7 built in
Storage: base: Cassette port (retained for compatibility, rarely used) · options: Internal 5.25" floppy disc drive (Master Compact and many fitted units) · ADFS via the 1 MHz bus or Winchester (hard disc) interface on the Turbo/ANFS boards
Os Support: latest: MOS 3.50 (final revision); ADFS and DFS filing systems in ROM · shipped: BBC BASIC IV with MOS 3.20, both in ROM; built-in View wordprocessor, ViewSheet spreadsheet, Edit, and Terminal applications in ROM
Release Price: £495

Variants

Models

Master 128The standard model: 128 KB RAM, full ROM application suite, numeric keypad.

Master Compact1986 cost-reduced redesign in a slimmer case with a built-in 3.5" floppy drive and a two-piece keyboard/base unit; dropped the Tube and 1 MHz bus edge connectors.

Master ETDiskless "Economatic" variant aimed at schools and networked classrooms via Econet, no floppy drive fitted.

Master TurboFitted with an internal 65C102 second processor board running at 4 MHz for roughly double the throughput.

Upgrade paths

CPU

Internal 65C102 second processor (Turbo upgrade) or external Tube-connected Z80/80186/ARM second processors · The Tube interface, carried over from the BBC Micro, let the Master offload processing to a second CPU; the Master 512 add-on used this to run DOS Plus on an 80186.

~£200 for the official Acorn Turbo board at the time

MODERATE

storage

Internal or external 5.25"/3.5" floppy drives under ADFS, or a Winchester hard disc via a third-party SCSI/ST506 interface · ADFS in ROM meant hard discs and double-sided drives worked without extra filing-system software, unlike the BBC Micro's DFS-only ROM set.

~£150-£300 for a drive and interface at the time

MODERATE

RAM

128 KB is fixed on the motherboard; the separate Master 512 card added 512 KB dedicated to its own 80186 co-processor, not shared with the 6502 side · Sideways RAM banks are used for ROM images and utilities rather than general program memory, same limitation as the BBC Micro.

n/a

LOCKED

other

Econet network module (fitted as standard on most units) for classroom file/printer sharing · Econet was ubiquitous in UK schools running Master fleets from a shared file server.

included on most units

EASY