Acorn BBC Micro Model B+ 64K

The Acorn BBC Micro Model B+ 64K revised the BBC motherboard with additional RAM, shadow-screen memory and a WD1770 floppy controller. It retained broad compatibility with the Model B while preparing several ideas used in the Master series.

The B+ was a short-lived bridge between the original BBC Micro and the BBC Master, and its altered board layout makes it a distinct model.

Notable Features

• Rockwell 6512 at 2 MHz forms the centre of the system.
• The standard memory and storage configuration was 64KB RAM including 20KB shadow screen memory and 12KB sideways RAM and Cassette and WD1770 floppy-disc controller.
• Its principal display arrangement was Television, composite video or RGB monitor.

Historical Significance

• The B+ was a short-lived bridge between the original BBC Micro and the BBC Master, and its altered board layout makes it a distinct model.
• This page represents a distinct Acorn model rather than a regional, memory-only or bundled-software variation.

Collector’s Notes

• Original keyboards, power supplies, manuals, expansion cards and storage hardware materially improve a surviving system.
• Internal revisions and dealer-installed upgrades mean an individual machine should be checked against its serial label and fitted hardware.

Specifications

Technical Information
Name	Acorn BBC Micro Model B+ 64K
Manufacturer	Acorn Computers
Launched	Saturday, June 1, 1985
Discontinued	1986
Country	United Kingdom
CPU	Rockwell 6512 at 2 MHz
Units Sold
Operating System	BBC MOS 2.00 with BBC BASIC II and DFS 2.10
I/O	BBC Micro display, serial, analogue, user, printer, 1 MHz bus, Tube and optional Econet interfaces
Keyboard	Integrated 74-key keyboard with ten function keys
Storage	Cassette and WD1770 floppy-disc controller
Sound	Texas Instruments SN76489; three tone channels plus noise
Graphics	Eight BBC display modes with shadow-screen support
Display	Television, composite video or RGB monitor
ROM	48KB OS, BBC BASIC and DFS ROM; sideways ROM sockets
RAM	64KB RAM including 20KB shadow screen memory and 12KB sideways RAM
CPU Speed	2 MHz