A BBC Micro expansion unit, for the
BBC Micro
The British Broadcasting Corporation Microcomputer System, or BBC Micro, is a series of microcomputers and associated peripherals designed and built by Acorn Computers in the 1980s for the BBC Computer Literacy Project. Designed with an emphas ...
is one of a number of peripherals in a box with the same profile and styling as the main computer.
Second Processors
![Acorn 6502 2nd processor (front & top)](https://upload.wikimedia.org/wikipedia/commons/c/ca/Acorn_6502_2nd_processor_%28front_%26_top%29.jpg)
The second processors are connected to Acorn's proprietary and trademarked
''Tube'' interface. Only one second processor unit could be connected at a time to a BBC Micro, although a Master 128 could also have a co-processor fitted internally at the same time.
The terminology of ''second'' processor was slightly misleading, since connected and switched on, the system worked on a "host-parasite" model, with the processor in the external unit taking control while the 6502 in the "main" computer simply took on responsibility for
I/O.
6502 Second Processor
![Acorn 6502 2nd processor with top cover removed](https://upload.wikimedia.org/wikipedia/commons/7/77/Acorn_6502_2nd_processor_with_top_cover_removed.jpg)
The 6502 Second Processor (using a
65C02
The Western Design Center (WDC) 65C02 microprocessor is an enhanced CMOS version of the popular nMOS-based 8-bit MOS Technology 6502. The 65C02 fixed several problems in the original 6502 and added some new instructions, but its main feature ...
) was clocked at 3 MHz, a full 50% faster than the 6502 inside a BBC Model B, and also had 64 KB of
RAM
Ram, ram, or RAM may refer to:
Animals
* A male sheep
* Ram cichlid, a freshwater tropical fish
People
* Ram (given name)
* Ram (surname)
* Ram (director) (Ramsubramaniam), an Indian Tamil film director
* RAM (musician) (born 1974), Dutch
* ...
, of which typically 30–44 KB was free for application data (compared to as little as 8.5 KB on an unexpanded Model B in graphics mode, or only 5.75 KB with the disc interface). A version of
BBC BASIC II, called Hi-BASIC, was delivered on ROM with this processor together with a DNFS ROM containing the latest versions of the disc filing system (DFS) and Econet network filing system (NFS). The product was launched with a price of £199.
The Bitstik CAD system,
originally developed by Robocom for the Apple II,
was offered as an accessory for the 6502 Second Processor, also requiring dual 80-track floppy drives. The Bitstik system itself was introduced with a price of around £375, which combined with floppy drives estimated at £500, the second processor at £199, the cost of the BBC Micro itself at £399, and the price of a colour monitor (Acorn recommending their own RGB monitor
), the total investment was estimated to be between £1500 to £2000 depending on any particular customer's existing equipment and preferences.
Featuring a three-axis joystick, offering the usual two-dimensional navigation plus a knob to control zooming, the software worked in the high-resolution four-colour display mode, providing support for the display and editing of scalable vector graphics. The dual-drive arrangement was necessary to allow the first drive to provide access to the utilities and for the second drive to act as a "drawing buffer".
The original Bitstik product had been introduced for the 64 KB
Apple II Plus
The Apple II Plus (stylized as Apple ] or apple plus) is the second model of the Apple II series of personal computers produced by Apple Computer. It was sold from June 1979 to December 1982. Approximately 380,000 II Pluses were sold during its ...
in 1982 at a price of £275 for the device and software itself, with a complete system costing around £2000. This was, however, considered "extremely good value", given that a "ready-to-use 'turnkey' drawing computer" would have cost £100,000 for a minicomputer-based system in 1980, and even at the start of 1982 could have cost £20,000. To realise the "full potential" of the solution, a plotter was recommended, although A3-sized plotters cost at least £1,000, with a Tektronix A2-sized model costing £6,500 but offering a precision of 0.001mm. In a review published in late 1982, the solution was regarded as "the most powerful drawing system available in Britain today for use on small computers".
By 1984, Robocom was claiming to be the UK's leading supplier of CAD solutions, with 2,500 users, and the Acorn-licensed version of the Bitstik solution offered a higher screen resolution, more colours, and better performance. At launch, only Acorn's own sparkjet printer was supported as an output device, however.
Various CAD programs were able to take advantage of the 6502 Second Processor, as was the second processor-specific version of
Elite (video game), Elite. Hi versions of View, WordWise and Intersheet were also produced.
Z80 Second Processor
The
Z80
The Z80 is an 8-bit microprocessor introduced by Zilog as the startup company's first product. The Z80 was conceived by Federico Faggin in late 1974 and developed by him and his 11 employees starting in early 1975. The first working samples were ...
Second Processor featured a Z80B CPU running at 6 MHz accessing 64 KB of RAM. It required the
floppy disc
A floppy disk or floppy diskette (casually referred to as a floppy, or a diskette) is an obsolescent type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined ...
upgrade and, being aimed at business, enabled the BBC system to run
CP/M programs. As noted in one review, with reference to the intended appeal of the BBC Micro to the home, education and business markets, with the Z80 second processor "Acorn have completed the BBC Microcomputer system as originally planned".
The product was launched in mid-1984 at a price of £299 and included an estimated £3000 worth of bundled software that included the CP/M 2.2 operating system itself (with GSX graphics), CIS Cobol and utilities from Microfocus, the Memo Plan, Graph Plan and File Plan office applications from Chang Laboratories, the Accountant and Nucleus packages from Compact Accounting Services, and two BASIC implementations: Z80 BBC BASIC and Mallard Professional BASIC.
Despite "a policy of continuous improvement", Acorn apparently abandoned plans to update the software bundle in mid-1986 due to a review of the CP/M market.
Other suppliers continued to support the Z80, delivering Z80 second processor hardware and software bundles, such as the Task-Master which combined an externally connected second processor, compatible with the BBC Model B, B+ and Master, and a suite of software including a CP/M 2.2-compatible operating system known as ZCPR3 and Borland's Turbo Pascal plus other development tools.
32016 Second Processor
Originally referred to as the Gluon, a
National Semiconductor 32016 second processor solution was apparently planned for the BBC Micro and for other 8-bit microcomputers, with the BBC Micro version employing the Tube interface and offering a quarter of a megabyte of RAM, whereas the "Universal Gluon" would be connected to a microcomputer acting as a terminal using a serial or parallel interface, offer up to 1 MB of RAM, up to 5 MB of hard disk storage, and either a minimal operating system or Unix.
Subsequent news of the second processor indicated the renaming of the product, dropping the Gluon name, the use of Acorn's own Panos operating system instead of Xenix, with availability in 1985.
The product that was eventually delivered is a sophisticated second processor expansion sometimes branded as "Acorn Cambridge Co-Processor" with an Acorn logo, and sometimes as "BBC Microcomputer System 32016 Second Processor" along with the BBC Micro's owl logo. The device uses the 32016 CPU and 32081 FPU running at 6 MHz. It runs the non-graphical
Panos operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...
. Various programming languages are available including
C,
FORTRAN,
Lisp, and
Pascal, in addition to a version of
BBC BASIC
BBC BASIC is a version of the BASIC programming language released in 1981 as the native programming language for the BBC Micro home/personal computer, providing a standardized language for a UK computer literacy project of the BBC. It was wr ...
. Initially offered as the 32016 Second Processor with 256 KB of RAM,
the expansion was subsequently delivered as the Cambridge Co-Processor with 512 KB or 1 MB of RAM as standard.
The 32016 second processor is also present as part of the ''Acorn Cambridge Workstation'' using an 8 MHz CPU
and 4 MB of RAM, sold as part of the
Acorn Business Computer line. Originally, Acorn had apparently sought to use CPUs rated for 10 MHz, but seemed to have settled for available parts as the different products were introduced. The second processor board was also able to use 64-kilobit or 256-kilobit RAM devices, thus allowing the earlier 256 KB specification to be upgraded to 1 MB as the higher-density devices became available and affordable.
Universal Second Processor Unit
The Universal Second Processor Unit was an adapter for BBC Master internal co-processor boards, to allow them to be used as external co-processors. It comprised a power supply, interface logic and a connector that matched the internal co-processor connector built into the BBC Master main board. This allowed the BBC B and B+ to use the Turbo board (4 MHz 65C102 with 64 KB of RAM) and the Master 512 board (10 MHz
80186
The Intel 80186, also known as the iAPX 186, or just 186, is a microprocessor and microcontroller introduced in 1982. It was based on the Intel 8086 and, like it, had a 16-bit external data bus multiplexed with a 20-bit address bus. The 80188 ...
with 512 KB of RAM), by fitting them into this expansion unit. It also allowed the BBC Master to have two internal co-processor boards connected, only one of which could be enabled through software. Watford Electronics sold a similar solution called the Co-Pro Adaptor.
ARM Evaluation System
The ARM Evaluation System was announced in July 1986 for fourth quarter availability at a cost of £4,500 plus VAT.
As one of the first production
RISC processors, the
ARM
In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between th ...
Evaluation System was part of the development programme leading to the
Acorn Archimedes
Acorn Archimedes is a family of personal computers designed by Acorn Computers of Cambridge, England. The systems are based on Acorn's own ARM architecture processors and the proprietary operating systems Arthur and RISC OS. The first mode ...
and its early
Arthur
Arthur is a common male given name of Brythonic origin. Its popularity derives from it being the name of the legendary hero King Arthur. The etymology is disputed. It may derive from the Celtic ''Artos'' meaning “Bear”. Another theory, more wi ...
operating system. It was not branded "BBC", but it is physically contained within the family's "cheese wedge" case. The ARM 1 processor was clocked at 8 MHz, and was fitted with 2 MB or 4 MB of RAM.
In 2006, a new ARM processor board using an ARM7TDMI processor was designed and sold, without an enclosure but able to fit within the original case.
Other Second Processors
Several other second processor solutions were produced by third party suppliers, typically employing a different style of casing than the standard expansion unit profile, with some using the 1 MHz bus instead of the Tube connector, and with others merely providing a conventional serial link.
Z80 second processors offering 64 KB of RAM and CP/M-compatible operating systems included the Multiform Z80 from Technomatic, priced at £299,
and several products from
Torch Computers
Torch Computers Ltd was a computer hardware company with origins in a 1982 joint venture between Acorn Computers and Climar Group that led to the development of the Communicator or C-series computer, a system based on the BBC Micro with a Z80 se ...
such as the Z80 Disc Pack (ZDP) and ZEP, the latter priced at around £340.
Torch also offered the Intel 8088-based Graduate running MS-DOS and having 256 KB of RAM and dual floppy drives, priced at £1000 plus VAT,
and the Z80- and 68000-based HDP68K or Unicorn, the latter running Unix and having 256 KB of RAM or more, floppy drive and 20 MB hard drive.
Various other 68000-based second processor solutions were offered, such as the Casper by CA Special Products,
the Cambridge Microprocessor Systems 68000 second processor,
the Flight Electronics 68000 processor board,
and the Micro Developments MD512k Universal Second Processor System.
Cumana chose to produce a 68008 second processor running the OS-9 operating system that was installed into the 6502 CPU socket, relocating the 6502 to the second processor board itself, and providing 512 KB RAM and its own disk controller. Initial pricing was announced as £695 plus VAT,
although subsequent recommended retail prices were around £800 for the upgrade board alone, with "particularly keenly priced" bundles of the board with 10 MB and 20 MB hard drives available for £900 and £1,000 respectively. Performance concerns associated with the 68008, due to experiences with the
Sinclair QL
The Sinclair QL (for ''Quantum Leap'') is a personal computer launched by Sinclair Research in 1984, as an upper-end counterpart to the ZX Spectrum. The QL was aimed at the serious home user and professional and executive users markets from small ...
, were alleviated through the presence of "plenty of sub processors", these utilised for managing peripherals including control of floppy and SASI-compatible hard drives, coupled with the use of a relatively fast 8 MHz CPU. Due to the method of interfacing the second processor to the host system, the board was also able to give the 68008 direct access to the host machine's user port, 1 MHz bus and analogue port, permitting the development of programs in languages like C to utilise these capabilities. Indeed, Cumana bundled an estimated £3000 worth of software with the board, including assembly language, BASIC, Pascal and C language tools, the "fourth generation language" Sculptor, word processing, spellchecking, mail merge, spreadsheet and database applications, plus a screen editor.
Cambridge Microprocessor Systems and Control Universal both offered 6809 second processor solutions supporting the FLEX operating system.
A 6809 second processor project had been pursued internally within Acorn,
leading to a tentative product that would offer better support for high-level languages,
but the product was not brought to market, with Acorn choosing to emphasise the 6502, whose performance was being steadily improved relative to the 6809.
Permanent Memory Systems produced a 6502 second processor, the B2P 6502, employing a 2 MHz 65C02 processor as opposed to the faster 6502 device used by the Acorn 6502 Second Processor unit together with 64 KB of RAM. Connecting to the Tube and 1 MHz bus connectors, the expansion did not use Acorn's Tube ULA and thus risked incompatibility with some software written for the Acorn unit, but the benefit of this approach was the B2P's more competitive price of around £100.
Adapters
The adapters connected to the BBC Micro's 1 MHz bus interface. Adapters could be
daisy-chained, allowing more than one to be fitted.
Teletext adapter
The
teletext
A British Ceefax football index page from October 2009, showing the three-digit page numbers for a variety of football news stories
Teletext, or broadcast teletext, is a standard for displaying text and rudimentary graphics on suitably equipp ...
-like "Mode 7" display mode inside the 8-bit BBC Micros made a broadcast teletext adapter an obvious expansion, and the BBC would broadcast
telesoftware
The term telesoftware was coined by W.J.G. Overington who invented the concept in 1974; it literally means “software at a distance” and it often refers to the transmission of programs for a microprocessor or home computer via broadcast telete ...
free over
Ceefax
Ceefax (, punning on "seeing facts") was the world's first teletext information service and a forerunner to the current BBC Red Button service. Ceefax was started by the BBC in 1974 and ended, after 38 years of broadcasting, at 23:32:19 BST ( ...
. The hardware and software design was created by Graham Toal.
The initial software to use the adapter was quite basic but the BBC decided to rewrite it and produced the Advanced Teletext System in conjunction with GIS. The new ROM software added several features including support for the new Fastext system, which introduced the four coloured buttons subsequently found almost ubiquitously on European remote controls, including the "red button" which remains a feature of digital television broadcasting. A software downloader was also provided in ROM, permitting access to software available via the broadcast medium known as telesoftware. The downloader could be accessed by pressing a function key, this initiating a search for a catalogue of available software and opening a menu displaying the catalogue. Various commands were also provided to access teletext and telesoftware features.
The adapter itself was mains powered with its own power switch matching the one on the BBC microcomputer. Connection to the computer was via a ribbon cable and the only other connector on the adapter was a female
75 ohm TV aerial (in) connector. The adapter contained four manual tuning wheels to receive signals from four different broadcast channels
Rear view of the adapter Once tuned, use of the adapter, including switching channels, was controlled via the computer. Teletext pages were displayed on the computer monitor.
Prestel adapter
The
Prestel
Prestel (abbrev. from press telephone), the brand name for the UK Post Office Telecommunications's Viewdata technology, was an interactive videotex system developed during the late 1970s and commercially launched in 1979. It achieved a maxim ...
adapter was essentially a
modem
A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by Modulation#Digital modulati ...
fitted into the "cheese wedge"-shaped case. It enabled the user to connect to Prestel
viewdata
Viewdata is a Videotex implementation. It is a type of information retrieval service in which a subscriber can access a remote database via a common carrier channel, request data and receive requested data on a video display over a separate c ...
services over a telephone line.
IEEE 488 interface
Allowed the BBC Micro to talk over an
IEEE-488
IEEE 488 is a short-range digital communications 8-bit parallel multi-master interface bus specification developed by Hewlett-Packard as HP-IB (Hewlett-Packard Interface Bus). It subsequently became the subject of several standards, and is ...
bus to specialised equipment. "Acorn" rather than "BBC" branded.
Econet bridge
Used to connect two
Econet
Econet was Acorn Computers's low-cost local area network system, intended for use by schools and small businesses. It was widely used in those areas, and was supported by a large number of different computer and server systems produced both by ...
segments together. An Econet bridge is capable of automatically learning a simple network topology and selectively forwarding packets from one LAN segment to the other using a simple routing table based on the contents of the network byte in the Econet packet.
The Econet bridge is unique among the cheese wedge expansions, in that it is a stand-alone device that does not require a BBC computer to operate.
References
External links
General
BeebMaster's Cheese Wedges
32016
Binary Dinosaurs 32016 co-processorAcorn Cambridge Co-Processor @ The Centre for Computing History
Acorn Cambridge Workstation
ARM Evaluation System
ARM Evaluation System picturesAcorn ARM Evaluation System @ The Centre for Computing History
{{DEFAULTSORT:Bbc Micro Expansion Units
Acorn Computers
Legacy hardware