BBC Master
Encyclopedia
The BBC Master was a home computer released by Acorn Computers
in early 1986. It was designed and built for the British Broadcasting Corporation (BBC) and was the successor to the BBC Micro Model B
. The Master 128 remained in production until 1993.
RAM as standard, alleviating the shortage of available RAM which had amongst other things discouraged use of the best graphics modes in the original design, and had two cartridge slots mounted above the new numerical keypad. Rather than the MOS Technology 6502
microprocessor
used by the Model B
it ran on the slightly improved 65SC12
: the cost of this CPU compatibility with the Model B was that the address bus was still only 16 bits, meaning that only 64 kB could be directly addressed at any one time and the remaining memory had to be paged in as required. However the 65SC12's extra instructions allowed a little more to be shoehorned into the OS
and BBC BASIC ROMs, limited by the memory architecture to 16 kB each.
Although the Master was intended to be compatible with "legally written" software for the older models, there were some problems running older programs, particularly games. Conversely, although few programs were ever targeted specifically at Master series machines (except the Master 512), many later BBC games (and Master versions of earlier classics such as Elite) included enhanced features which took advantage of the extra memory.
The Master was available in several different models.
.
coprocessor card (which could be either bought with the machine or added to an existing Master 128).
interface and a VFS (Videodisc Filing System) ROM added, and formed the basis of the BBC Domesday System
. Although normally supplied as part of a Domesday System, with LaserVision
player, Domesday videodisc
s, monitor and trackerball
included, an upgrade kit was also available to turn a normal BBC Master into a Domesday System.
and Composite video
, plus an Econet
interface module and ANFS fitted as standard (it was usually an option). It used the same main circuit board as the Master 128, but the components for missing interfaces were simply not fitted (though there was nothing stopping them being added later by someone with appropriate soldering skills). The internal ROM
also contained much less software than that of the Master 128.
and 512 kB memory. It also had the ability to run DOS Plus
and the GEM
graphical user interface.
where available).
The unit under the monitor housed a 3½” floppy disk
drive and the system power supply. The remainder of the system was housed in the same unit as the keyboard, much like a conventional Master 128. The cartridge and cassette ports were removed as a space saving measure, and RS-232
hardware not populated on the circuit board as standard. A multifunction mouse and joystick port was provided as a 9 pin D type
with its function configured in software.
Software for the Compact was comparatively expensive (typically £20 for a game) due to the much lower demand for the 3½” disk format (5¼" was the standard for the Master and earlier BBC Micro
).
The Compact included Acorn's first public GUI
. Little commercial software, beyond that included on the Welcome disk, was ever made available for the system.
Several of the inputs were directly wired to specific registers in order to allow the hardware to do some of the heavy lifting. For example the light-pen input would directly halt a counter which was started by the start of the vertical sweep of each display refresh, making calculation of where the lightpen was touching the screen little more than a simple divide/remainder operation. Likewise, the motor control relay for the audio cassette tape was controlled by a simple command and could be readily used in numerous control applications.
Acorn Computers
Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were especially popular in the UK. These included the Acorn Electron, the BBC Micro, and the Acorn Archimedes...
in early 1986. It was designed and built for the British Broadcasting Corporation (BBC) and was the successor to the BBC Micro Model B
BBC Micro
The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...
. The Master 128 remained in production until 1993.
Design
The Master featured several improvements on its predecessor. The systems had 128 kBKilobyte
The kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information...
RAM as standard, alleviating the shortage of available RAM which had amongst other things discouraged use of the best graphics modes in the original design, and had two cartridge slots mounted above the new numerical keypad. Rather than the MOS Technology 6502
MOS Technology 6502
The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle and Bill Mensch for MOS Technology in 1975. When it was introduced, it was the least expensive full-featured microprocessor on the market by a considerable margin, costing less than one-sixth the price of...
microprocessor
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
used by the Model B
BBC Micro
The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...
it ran on the slightly improved 65SC12
WDC 65C02
The Western Design Center WDC 65C02 microprocessor is an upgraded CMOS version of the popular NMOS-based MOS Technology 6502 8-bit CPU — the CMOS redesign being made by Bill Mensch of the Western Design Center...
: the cost of this CPU compatibility with the Model B was that the address bus was still only 16 bits, meaning that only 64 kB could be directly addressed at any one time and the remaining memory had to be paged in as required. However the 65SC12's extra instructions allowed a little more to be shoehorned into the OS
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
and BBC BASIC ROMs, limited by the memory architecture to 16 kB each.
Although the Master was intended to be compatible with "legally written" software for the older models, there were some problems running older programs, particularly games. Conversely, although few programs were ever targeted specifically at Master series machines (except the Master 512), many later BBC games (and Master versions of earlier classics such as Elite) included enhanced features which took advantage of the extra memory.
Models
Master 128
This was the standard issue computer. The 128 in the name referred to its 128 kB of RAM, though it also featured 128 kB ROMRead-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
.
Master Turbo
This was a Master with 4 MHz 65C102WDC 65C02
The Western Design Center WDC 65C02 microprocessor is an upgraded CMOS version of the popular NMOS-based MOS Technology 6502 8-bit CPU — the CMOS redesign being made by Bill Mensch of the Western Design Center...
coprocessor card (which could be either bought with the machine or added to an existing Master 128).
Master AIV
The Master AIV (Advanced Interactive Videodisc) was essentially a Master Turbo model with a SCSISCSI
Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it...
interface and a VFS (Videodisc Filing System) ROM added, and formed the basis of the BBC Domesday System
BBC Domesday Project
The BBC Domesday Project was a partnership between Acorn Computers Ltd, Philips, Logica and the BBC to mark the 900th anniversary of the original Domesday Book, an 11th century census of England...
. Although normally supplied as part of a Domesday System, with LaserVision
Laserdisc
LaserDisc was a home video format and the first commercial optical disc storage medium. Initially licensed, sold, and marketed as MCA DiscoVision in North America in 1978, the technology was previously referred to interally as Optical Videodisc System, Reflective Optical Videodisc, Laser Optical...
player, Domesday videodisc
Videodisc
Videodisc is a general term for a laser- or stylus-readable random-access circular disc that contains both audio and analog video signals recorded in an analog form...
s, monitor and trackerball
Trackball
A trackball is a pointing device consisting of a ball held by a socket containing sensors to detect a rotation of the ball about two axes—like an upside-down mouse with an exposed protruding ball. The user rolls the ball with the thumb, fingers, or the palm of the hand to move a cursor...
included, an upgrade kit was also available to turn a normal BBC Master into a Domesday System.
Master ET
The ET (Econet Terminal) system was designed for use in a network and as such had no interfaces except RGBRGB color model
The RGB color model is an additive color model in which red, green, and blue light is added together in various ways to reproduce a broad array of colors...
and Composite video
Composite video
Composite video is the format of an analog television signal before it is combined with a sound signal and modulated onto an RF carrier. In contrast to component video it contains all required video information, including colors in a single line-level signal...
, plus an Econet
Econet
Econet was Acorn's low-cost local area network system, intended for use by schools and small businesses. Econet is rumoured to be an abbreviation of Economy Network, but Acorn were always careful to stress the Greek root, oikos, meaning "house"....
interface module and ANFS fitted as standard (it was usually an option). It used the same main circuit board as the Master 128, but the components for missing interfaces were simply not fitted (though there was nothing stopping them being added later by someone with appropriate soldering skills). The internal ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
also contained much less software than that of the Master 128.
Master 512
This system boasted a coprocessor card with a 10 MHz Intel 80186Intel 80186
The 80188 is a version with an 8-bit external data bus, instead of 16-bit. This makes it less expensive to connect to peripherals. The 80188 is otherwise very similar to the 80186. It has a throughput of 1 million instructions per second....
and 512 kB memory. It also had the ability to run DOS Plus
DOS Plus
DOS Plus is an operating system written by Digital Research, first released in 1985. It can be seen as an intermediate step between CP/M-86 and DR-DOS....
and the GEM
Graphical Environment Manager
GEM was a windowing system created by Digital Research, Inc. for use with the CP/M operating system on the Intel 8088 and Motorola 68000 microprocessors...
graphical user interface.
Master Scientific
The Master Scientific was announced at the time of the BBC Master's launch, but was not produced. It was to have an 8 MHz 32016 coprocessor with 32081 floating point processor and 512 kB of RAM, running the PANOS operating system. This was similar to the previous external 32016 Second Processor.Master Compact
This model separated the keyboard from another unit which could be placed under the monitor. Only the ADFS filing system was supplied as standard, though it is possible to load a 1770 DFS ROM into sideways RAM, or to insert a ROM or EPROM containing it. The Compact also utilised a limited re-burn EEPROM, instead of the battery backed clock plus CMOS memory found in the other models, and hence had no real time clock of its own (the time could be fetched via EconetEconet
Econet was Acorn's low-cost local area network system, intended for use by schools and small businesses. Econet is rumoured to be an abbreviation of Economy Network, but Acorn were always careful to stress the Greek root, oikos, meaning "house"....
where available).
The unit under the monitor housed a 3½” floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
drive and the system power supply. The remainder of the system was housed in the same unit as the keyboard, much like a conventional Master 128. The cartridge and cassette ports were removed as a space saving measure, and RS-232
RS-232
In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...
hardware not populated on the circuit board as standard. A multifunction mouse and joystick port was provided as a 9 pin D type
D-subminiature
The D-subminiature or D-sub is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. When they were introduced, D-subs were among the smaller connectors used on computer systems....
with its function configured in software.
Software for the Compact was comparatively expensive (typically £20 for a game) due to the much lower demand for the 3½” disk format (5¼" was the standard for the Master and earlier BBC Micro
BBC Micro
The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...
).
The Compact included Acorn's first public GUI
Graphical user interface
In computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...
. Little commercial software, beyond that included on the Welcome disk, was ever made available for the system.
Specifications
- 2 MHz RockwellRockwell- People :* Dick Rockwell, an American comic strip and comic book artist, nephew of Norman Rockwell* Francis W. Rockwell, a United States Congressman from Massachusetts* Francis W...
R65SC12WDC 65C02The Western Design Center WDC 65C02 microprocessor is an upgraded CMOS version of the popular NMOS-based MOS Technology 6502 8-bit CPU — the CMOS redesign being made by Bill Mensch of the Western Design Center...
processor - 128 kB ROMRead-only memoryRead-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
in the Master 128, Master Turbo, and Master 512. Comprising a 16 kB MOS (Machine Operating System), always accessible, and seven 16 kB sidewaysSideways address spaceThe "Sideways" address space on the Acorn BBC Microcomputer and Master-series microcomputer was Acorn's bank switching implementation, providing for permanent system expansion in the days before hard disk drives or even floppy disk drives were commonplace...
ROMs, any one of which could be paged into memory at a time:- 16 kB Terminal emulator and MOS extras (such as the cassette filing system) in paged ROM 15
- 16 kB Acornsoft View (word processor) in paged ROM 14
- 16 kB Advanced Disc Filing SystemAdvanced Disc Filing SystemThe Advanced Disc Filing System is a computing file system particular to the Acorn computer range and RISC OS based successors. Initially based on the rare Acorn Winchester Filing System, it was renamed to the Advanced Disc Filing System when support for floppy discs was added and on later 32 bit...
in paged ROM 13 - 16 kB BBC BASIC in paged ROM 12
- 16 kB Acorn Screen Editor AKA Edit (text/BBC BASIC editor) in paged ROM 11
- 16 kB ViewSheetViewSheetViewSheet was a spreadsheet program produced in the 1980s by Acorn Computers for use with their series of microcomputers. It was distributed as a pre-installed ROM with some computer models. ViewSheet was written by Mark Colton.-Description:...
(spreadsheet) in paged ROM 10 - 16 kB Disc Filing SystemDisc Filing SystemThe Disc Filing System is a computer file system developed by Acorn Computers Ltd, and introduced in 1982 for the Acorn BBC Microcomputer. It was shipped as a ROM to be inserted onto the BBC Micro's motherboard. It has an extremely limited design, and uses a flat directory structure...
and Sideways RAM utilities in paged ROM 9
- 64 kB ROMRead-only memoryRead-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
in the Master ET. Comprising a 16 kB MOS (Machine Operating System), always accessible, and three 16 kB sidewaysSideways address spaceThe "Sideways" address space on the Acorn BBC Microcomputer and Master-series microcomputer was Acorn's bank switching implementation, providing for permanent system expansion in the days before hard disk drives or even floppy disk drives were commonplace...
ROMs, any one of which could be paged into memory at a time:- 16 kB MOS extras (such as the cassette filing system and Sideways RAM utilities) in paged ROM 15
- 16 kB Advanced Network Filing SystemEconetEconet was Acorn's low-cost local area network system, intended for use by schools and small businesses. Econet is rumoured to be an abbreviation of Economy Network, but Acorn were always careful to stress the Greek root, oikos, meaning "house"....
in paged ROM 14 - 16 kB BBC BASIC in paged ROM 13
- 128 kB RAM, comprising:
- 32 kB main user program/data storage
- 20 kB "shadowShadow RAM (Acorn)"Shadow RAM", on the Acorn BBC Microcomputer and Master-series microcomputer is a special framebuffer implementation to free up main memory and permit double-buffered graphics....
" video memory (paged over main user RAM) - 12 kB OS workspace (paged over ROM)
- 64 kB workspace accessible to user machine code applications (divided into up to four 16 kB regions to act like volatile paged ROMs)
- Full-travel keyboardComputer keyboardIn computing, a keyboard is a typewriter-style keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches...
with a top row of ten red-orange function keyFunction keyA function key is a key on a computer or terminal keyboard which can be programmed so as to cause an operating system command interpreter or application program to perform certain actions...
s
and AT-style numeric keypad. The 'BREAK' reset key could be physically disabled by rotating a small plastic camCamA cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice-versa. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path...
, particularly useful in educational environments - Highly configurable graphics display based on the Motorola 6845Motorola 6845The Motorola 6845 is a video address generator first introduced by Motorola and used among others in the Videx VideoTerm display cards for the Apple II computers, the MDA and CGA video adapters for the IBM PC, in the Amstrad CPC and the BBC Micro. Its functionality was duplicated and extended by...
. Unlike on the original BBC MicroBBC MicroThe BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...
, separate video RAM was used so that choosing a high-resolution mode did not reduce the amount of available user RAM. (However, user RAM could still be used as the video buffer if required, in order to allow effects such as double bufferingDouble bufferingIn computer science, multiple buffering is the use of more than one buffer to hold a block of data, so that a "reader" will see a complete version of the data, rather than a partially-updated version of the data being created by a "writer"...
.) Eight graphics modes were provided by the system ROM:- Modes 0 to 6 could display a choice of colours from a logical palette of sixteen, though only eight physical colours could really be generated by the hardware; the eight RGBRGB color modelThe RGB color model is an additive color model in which red, green, and blue light is added together in various ways to reproduce a broad array of colors...
colours (black, red, green, yellow, blue, magenta, cyan, white) and said colours in a flashing state; - Modes 3 and 6 were special software (framebuffer) text modes. To save RAM, the count of lines was reduced from 32 to 25. As this would reduce the height of the frame, filler rows were created between each line of text when the frame was output, where no pixels were read from the framebuffer. This creates characteristic black lines between the rows of text when a different background colour is set, and a blank gap at the bottom of the display with the left-over pixels. The screen mode is otherwise held in memory as a regular graphics mode.
- Mode 7's TeletextTeletextTeletext is a television information retrieval service developed in the United Kingdom in the early 1970s. It offers a range of text-based information, typically including national, international and sporting news, weather and TV schedules...
capability was provided by a Mullard SAA5050Mullard SAA5050The Mullard SAA5050 was a character generator chip for implementing the teletext character set. The SAA5050 was used in teletext-equipped television sets, viewdata terminals, and microcomputers, most notably the Philips P2000T homecomputer , Acorn's System 2 , and the BBC micro's...
Teletext chip.
- Modes 0 to 6 could display a choice of colours from a logical palette of sixteen, though only eight physical colours could really be generated by the hardware; the eight RGB
- Four independent sound channels (one noise and 3 melodic) using the Texas Instruments SN76489Texas Instruments SN76489The SN76489 Digital Complex Sound Generator is a TTL-compatible Programmable Sound Generator chip from Texas Instruments. It contains three square wave tone generators and one white noise generator, each of which can produce sounds at various frequencies and sixteen different volume levels...
sound chipSound chipA sound chip is an integrated circuit designed to produce sound . It might be doing this through digital, analog or mixed-mode electronics... - Built-in hardware support included:
- pluggable ROMs, directly or via cartridge slots
- floppy disc drives (both DFSDisc Filing SystemThe Disc Filing System is a computer file system developed by Acorn Computers Ltd, and introduced in 1982 for the Acorn BBC Microcomputer. It was shipped as a ROM to be inserted onto the BBC Micro's motherboard. It has an extremely limited design, and uses a flat directory structure...
and the newer ADFSAdvanced Disc Filing SystemThe Advanced Disc Filing System is a computing file system particular to the Acorn computer range and RISC OS based successors. Initially based on the rare Acorn Winchester Filing System, it was renamed to the Advanced Disc Filing System when support for floppy discs was added and on later 32 bit...
supported) with WD1770 disc controller - tape interface (with motor control), using a variation of the Kansas City standardKansas City standardThe Kansas City Standard , or Byte standard, is a digital data format for audio cassette drives. Byte magazine sponsored a symposium in November 1975 in Kansas City, Missouri to develop a standard for storage of digital computer data on inexpensive consumer quality cassettes, at a time when...
data encoding scheme - parallel printer port (CentronicsCentronicsCentronics Data Computer Corporation was a pioneering American manufacturer of computer printers, now remembered primarily for the parallel interface that bears its name.-The beginning:Centronics began as a division of Wang Laboratories...
compatible) - serial communication (using RS-423RS-423RS/EIA/TIA-423 is a standard for serial communications. It defines an unbalanced interface , with a single, unidirectional sending driver, and allows for up to 10 receivers . It is normally implemented in integrated circuit technology and can also be employed for the interchange of serial binary...
, a superset of RS-232RS-232In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...
) - display output for TV, RGB or 1v p-p video monitor
- a 15 pin 'D shaped' port with four analogue inputs (suitable for two joystickJoystickA joystick is an input device consisting of a stick that pivots on a base and reports its angle or direction to the device it is controlling. Joysticks, also known as 'control columns', are the principal control in the cockpit of many civilian and military aircraft, either as a center stick or...
s, four digital/contact ports (for buttons) and a special Light penLight penA light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's CRT TV set or monitor. It allows the user to point to displayed objects, or draw on the screen, in a similar way to a touch screen but with greater positional accuracy...
input - proprietary "Tube" interface for internal or external second CPU (in the Master 512 model, an 80186Intel 80186The 80188 is a version with an 8-bit external data bus, instead of 16-bit. This makes it less expensive to connect to peripherals. The 80188 is otherwise very similar to the 80186. It has a throughput of 1 million instructions per second....
was used; other options included a 3 MHz extra 6502MOS Technology 6502The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle and Bill Mensch for MOS Technology in 1975. When it was introduced, it was the least expensive full-featured microprocessor on the market by a considerable margin, costing less than one-sixth the price of...
, a Zilog Z80Zilog Z80The Zilog Z80 is an 8-bit microprocessor designed by Zilog and sold from July 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for military purposes...
for e.g. CP/M, an NS32016NS320xxThe 320xx or NS32000 was a series of microprocessors from National Semiconductor . They were likely the first 32-bit general-purpose microprocessors on the market, but due to a number of factors never managed to become a major player...
, an ARM1ARM architectureARM is a 32-bit reduced instruction set computer instruction set architecture developed by ARM Holdings. It was named the Advanced RISC Machine, and before that, the Acorn RISC Machine. The ARM architecture is the most widely used 32-bit ISA in numbers produced...
, and others) - a 16 pin IDC style "user port" consisting of 8 general purpose digital I/O pins (and two special handshakingHandshakingIn information technology, telecommunications, and related fields, handshaking is an automated process of negotiation that dynamically sets parameters of a communications channel established between two entities before normal communication over the channel begins...
ones) mapped directly into the 6522 VIA - generic expansion through the "1 MHz bus", and
- EconetEconetEconet was Acorn's low-cost local area network system, intended for use by schools and small businesses. Econet is rumoured to be an abbreviation of Economy Network, but Acorn were always careful to stress the Greek root, oikos, meaning "house"....
interface, installed by adding a module board and the ANFS ROM (fitted as standard to the Master ET machine)
Several of the inputs were directly wired to specific registers in order to allow the hardware to do some of the heavy lifting. For example the light-pen input would directly halt a counter which was started by the start of the vertical sweep of each display refresh, making calculation of where the lightpen was touching the screen little more than a simple divide/remainder operation. Likewise, the motor control relay for the audio cassette tape was controlled by a simple command and could be readily used in numerous control applications.