View source for BBC Micro expansion unit

{{Lead too short|date=January 2024}}
[[Image:BBC Teletext Adapter.jpg|thumb|Teletext Adapter alongside a BBC Model B]]

A '''BBC Micro expansion unit''', for the [[BBC Micro]] is one of a number of peripherals in a box with the same profile and styling as the main computer.

==Second processors==
[[File:Acorn 6502 2nd processor (front & top).jpg|thumb|upright|6502 Second Processor]]
The second processors are connected to Acorn's proprietary and trademarked [[Tube (BBC Micro)|''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.<ref name="acornuser198602">{{ cite news | url=https://archive.org/details/AcornUser043-Feb86/page/n12/mode/1up | title=Plug-in boards boost power | work=Acorn User | date=February 1986 | accessdate=8 November 2020 | page=11 }}</ref> 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===
[[File:Acorn 6502 2nd processor with top cover removed.jpg|thumb|left|upright|Interior of the 6502 Second Processor]]
The 6502 Second Processor (using a [[6502C]]) was clocked at 3&nbsp;MHz, a full 50% faster than the 6502 inside a BBC Model B, and also had 64&nbsp;KB of [[random-access memory|RAM]], of which typically 30–44&nbsp;KB was free for application data (compared to as little as 8.5&nbsp;KB on an unexpanded Model B in graphics mode, or only 5.75&nbsp;KB with the disc interface). A version of [[BBC BASIC|BBC BASIC II]], called Hi-BASIC, was delivered on [[read-only memory|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.<ref name="acornuser198405a">{{cite news | url=https://archive.org/details/AcornUser022-May84/page/n40/mode/1up| title=New Dimension in Time and Space? | work=Acorn User | date=May 1984 | accessdate=8 November 2020 | last1=Williamson | first1=Clive | pages=39, 84 }}</ref>

The Bitstik [[CAD]] system,<ref name="bitstik">{{ cite book | url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/Brochures/Acorn_AMP14_Bitstik.pdf | title=For ideas that can multiply... | publisher=Acorn Computers Limited }}</ref> originally developed by Robocom for the [[Apple II]],<ref name="nzbb198404">{{ cite news | url=https://archive.org/details/nzbitsandbytes-2-07/page/n55/mode/1up | title=Low cost step into design | work=Bits & Bytes | date=April 1984 | accessdate=11 November 2020 | last1=Simpson | first1=Richard | page=42 }}</ref> was offered as an accessory for the 6502 Second Processor, also requiring dual 80-[[disk track|track]] [[floppy drive]]s. 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 [[Component_video#RGB_analog_component_video|RGB]] monitor<ref name="bitstik" />{{rp|page=2}}), the total investment was estimated to be between £1500 and £2000 depending on any particular customer's existing equipment and preferences.<ref name="abcomputing198408">{{ cite news | url=https://archive.org/details/AB_Computing_1984-08_OCR/page/n41/mode/2up | title=Processor Progress | work=A&B Computing | last1=Webb | first1=Mark | date=August 1984 | accessdate=8 November 2020 | pages=42–46 }}</ref> 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".<ref name="acornuser198405b">{{ cite news | url=https://archive.org/details/AcornUser022-May84/page/n28/mode/1up | title=CAD Within Your Grasp | work=Acorn User | date=May 1984 | accessdate=8 November 2020 | last1=Mudge | first1=Robin | pages=27–29, 98 }}</ref>

The original Bitstik product had been introduced for the 64&nbsp;KB [[Apple II Plus]] 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".<ref name="design198209_bitstik">{{ cite magazine | url=https://archive.org/details/sim_design_1982-09_405/page/61/mode/1up | title=Apple Graphics on a Stick | magazine=Design | date=September 1982 | access-date=22 March 2022 | last1=Gibbs | first1=Tony | pages=61 }}</ref> 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.<ref name="design198406_bitstik">{{ cite magazine | url=https://archive.org/details/sim_design_1984-06_426/page/n65/mode/1up | title=Acorn Bitstik | magazine=Design | date=June 1984 | access-date=22 March 2022 | last1=Pipes | first1=Alan | pages=64 }}</ref>

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 [[Zilog Z80|Z80]] Second Processor featured a Z80B CPU running at 6&nbsp;MHz accessing 64&nbsp;KB of RAM. It required the [[floppy disc]] 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".<ref name="abcomputing198408" />

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 [[GEM_(desktop_environment)#GSX|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.<ref name="acornuser198406">{{ cite news | url=https://archive.org/details/AcornUser023-Jun84/page/n27/mode/2up | title=Business Bundle | work=Acorn User | date=June 1984 | accessdate=25 October 2020 | pages=26–27, 31 }}</ref>

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.<ref name="acornuser198608">{{ cite news | url=https://archive.org/details/AcornUser049-Aug86/page/n160/mode/1up | title=Acorn drops Z80 upgrade | work=Acorn User | date=August 1986 | accessdate=25 October 2020 | page=159 }}</ref>
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.<ref name="acornuser198707_taskmaster">{{ cite magazine | url=https://archive.org/details/AcornUser060-Jul87/page/n16/mode/1up | title=Z80 Task-Master | magazine=Acorn User | date=July 1987 | access-date=5 October 2022 | pages=15 }}</ref>

===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]] [[microcomputer]]s, 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 emulator|terminal]] using a [[serial communications|serial]] or [[parallel communications|parallel]] interface, offer up to 1&nbsp;MB of RAM, up to 5&nbsp;MB of hard disk storage, and either a minimal operating system or [[Unix]].<ref name="practicalcomputing198210">{{ cite news | url=http://chrisacorns.computinghistory.org.uk/docs/Mags/PC/PC_Oct82_CCurry.pdf | title=Chris Curry of Acorn | work=Practical Computing | date=October 1982 | accessdate=18 October 2020 | pages=62–63, 69, 71 }}</ref> 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.<ref name="acornuser198412">{{ cite news | url=https://archive.org/details/AcornUser029-Dec84/page/n11/mode/1up | title=Add-ons out..almost | work=Acorn User | date=December 1984 | accessdate=25 October 2020 | page=10 }}</ref>

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 [[Floating-point unit|FPU]] running at 6&nbsp;MHz. It runs the non-graphical [[Panos (operating system)|Panos]] [[operating system]]. Various [[programming language]]s are available including [[C (programming language)|C]], [[FORTRAN]], [[Lisp (programming language)|Lisp]], and [[Pascal (programming language)|Pascal]], in addition to a version of [[BBC BASIC]]. Initially offered as the 32016 Second Processor with 256&nbsp;KB of RAM,<ref name="acorn_APP31">{{ cite book | url=https://www.4corn.co.uk/archive/docs/AMPAPP/150/APP031%20-%2032016%20Second%20Processor-opt.pdf | title=The British Broadcasting Corporation Microcomputer 32016 Second Processor | publisher=Acorn Computers Limited | accessdate=10 October 2020 }}</ref> the expansion was subsequently delivered as the Cambridge Co-Processor with 512&nbsp;KB or 1&nbsp;MB of RAM as standard.<ref name="acorn_ccp_userguide">{{ cite book | url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/Sci/AcornScientific_CambridgeCoProUG.pdf | title=Cambridge Co-Processor User Guide | publisher=Acorn Computers Limited | date=July 1985 | issue=1 | page=5 }}</ref>

The 32016 second processor is also present as part of the ''Acorn Cambridge Workstation'' using an 8&nbsp;MHz CPU<ref name="practicalcomputing198510">{{ cite news | url=http://chrisacorns.computinghistory.org.uk/docs/Mags/PC/PC_Oct85_32016.pdf | title=Cambridge 32016 Co-Processor | work=Practical Computing | date=October 1985 | accessdate=18 October 2020 | last1=Cullis | first1=Roger | quote=The 32016 processor is clocked at 6MHz, compared with 8MHz on the Cambridge Workstation. }}</ref> and 4&nbsp;MB of RAM, sold as part of the [[Acorn Business Computer]] line. Originally, Acorn had apparently sought to use CPUs rated for 10&nbsp;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&nbsp;KB specification to be upgraded to 1&nbsp;MB as the higher-density devices became available and affordable.<ref name="acornuser198407">{{cite news | url=https://archive.org/details/AcornUser024-Jul84/page/n8/mode/1up | title=Acorn dispels superchip doubt | work=Acorn User | date=July 1984 | accessdate=28 August 2020 | page=7}}</ref>

===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&nbsp;MHz 65C102 with 64&nbsp;KB of RAM) and the Master 512 board (10&nbsp;MHz [[80186]] with 512&nbsp;KB of RAM), by fitting them into this expansion unit.<ref name="acorn_app111">{{ cite book | url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/Brochures/Acorn_APP111_UniversalSecondProcessor.pdf | title=Universal Second Processor | publisher=Acorn Computers Limited | date=1987 | access-date=4 June 2023 }}</ref> 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.<ref name="abcomputing198708">{{ cite news | url=https://archive.org/details/AB_Computing_1987-08_OCR/page/n8/mode/1up | title=BBC to PC by Tube | work=A&B Computing | last1=Taylor | first1=Gordon | date=August 1987 | accessdate=8 November 2020 | pages=9–11 }}</ref>

===ARM evaluation system===
The ARM Evaluation System was announced in July 1986 for fourth quarter availability at a cost of £4,500 plus VAT.<ref name="arm_evaluation_pr">{{ cite press release | url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/PR/Acorn_announces_the_ARM_Evaluation_kit.pdf | title=Acorn Computers Announce the Availability of an Evaluation System for Their Single Chip, 32-Bit Reduced Instruction Set Computer – the ARM | date=7 July 1986 | access-date=14 February 2021 }}</ref> As one of the first production [[RISC]] processors, the [[ARM architecture|ARM]] Evaluation System was part of the development programme leading to the [[Acorn Archimedes]] and its early [[Arthur (operating system)|Arthur]] operating system. It was not branded "BBC", but it is physically contained within the family's "cheese wedge" case. The [[List of ARM processors|ARM 1]] processor was clocked at 8&nbsp;MHz, and was fitted with 2&nbsp;MB or 4&nbsp;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.<ref>{{cite web|title=Sprow's webpages - Internal or external ARM coprocessor|url=http://www.sprow.co.uk/bbc/armcopro.htm|accessdate=2 March 2019}}</ref>

===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&nbsp;MHz bus instead of the Tube connector, and with others merely providing a conventional serial link.

Z80 second processors offering 64&nbsp;KB of RAM and CP/M-compatible operating systems included the Multiform Z80 from Technomatic, priced at £299,<ref name="acornuser198610a">{{ cite news | url=https://archive.org/details/AcornUser051-Oct86/page/n144/mode/1up | title=Improve Your Memory | work=Acorn User | last1=Brown | first1=Ed | date=October 1986 | accessdate=3 December 2020 | pages=143, 145 }}</ref> and several products from [[Torch Computers]] such as the Z80 Disc Pack (ZDP) and ZEP, the latter priced at around £340.<ref name="acornuser198504">{{ cite news | url=https://archive.org/details/AcornUser033-Apr85/page/n142/mode/1up | title=Can the ZEP 100 Zap the Acorn Z80? | work=Acorn User | last1=Williams | first1=Simon | date=April 1985 | accessdate=8 October 2020 | pages=141, 143–144 }}</ref>

Torch also offered the [[Intel 8088]]-based Graduate running [[MS-DOS]] and having 256&nbsp;KB of RAM and dual floppy drives, priced at £1000 plus VAT,<ref name="pcw198506">{{ cite news | url=https://archive.org/details/PersonalComputerWorld1985-06/page/162/mode/2up | title=Torch Graduate | last1=Vogler | first1=Jon | work=Personal Computer World | date=June 1985 | accessdate=6 October 2020 | pages=162–163 }}</ref> and the Z80- and [[Motorola 68000|68000]]-based HDP68K or Unicorn, the latter running Unix and having 256&nbsp;KB of RAM or more, floppy drive and 20&nbsp;MB [[hard drive]].<ref name="acornuser198409">{{ cite news | url=https://archive.org/details/AcornUser026-Sep84/page/n154/mode/1up | title=Unicorn: Cheapest Route to Unix | last1=Cummins | first1=Andrew | last2=Voke | first2=Peter | work=Acorn User | date=September 1984 | accessdate=6 October 2020 | pages=139, 141, 165 }}</ref>

Various other 68000-based second processor solutions were offered, such as the Casper by CA Special Products,<ref name="acornuser198612">{{ cite news | url=https://archive.org/details/AcornUser053-Dec86/page/n16/mode/1up | title=News in brief | work=Acorn User | date=December 1986 | accessdate=31 October 2020 | page=15 }}</ref> the Cambridge Microprocessor Systems 68000 second processor,<ref name="acornuser198703">{{ cite news | url=https://archive.org/details/AcornUser056-Mar87/page/n16/mode/1up | title=News in brief | work=Acorn User | date=March 1987 | accessdate=31 October 2020 | page=15 }}</ref> the Flight Electronics 68000 processor board,<ref name="acornuser198706">{{ cite news | url=https://archive.org/details/AcornUser059-Jun87/page/n8/mode/1up | title=BBC take Flight | work=Acorn User | date=June 1987 | accessdate=31 October 2020 | page=7 }}</ref> and the Micro Developments MD512k Universal Second Processor System.<ref name="acornuser198610">{{ cite news | url=https://archive.org/details/AcornUser051-Oct86/page/n102/mode/1up | title=High Speed CP/M Compatibility at Low Cost with the MD512k Universal Second Processor System | work=Acorn User | date=October 1986 | accessdate=31 October 2020 | page=101 }}</ref>

Although Acorn never released a 68000 second processor product, Acorn's co-founder, [[Christopher Curry (businessman)|Chris Curry]], speculated on the nature of a 68000-based second processor product utilising its predecessor to the BBC Micro, the Proton. Indicating the need for "quite a full Proton system" acting as a front end to a 68000-based unit, the tentative projected cost of the Proton system was thought to be around £{{Format price|450|0}}, with the expansion unit costing around £{{Format price|1000}}, offering 256&nbsp;KB or 512&nbsp;KB of RAM. The Unix and [[TRIPOS]] operating systems were considered to be likely candidates to run on the expansion.<ref name="personalcomputerworld198104_acorn">{{ cite magazine | url=https://archive.org/details/PersonalComputerWorld1981-04/page/40/mode/1up | title=Acorn's growing | magazine=Personal Computer World | last1=Kewney | first1=Guy | date=April 1981 | access-date=15 May 2024 | pages=40 }}</ref>

Cumana chose to produce a [[Motorola 68008|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&nbsp;KB RAM and its own [[disk controller]]. Initial pricing was announced as £695 plus VAT,<ref name="acornuser198511">{{ cite news | url=https://archive.org/details/AcornUser040-Nov85/page/n10/mode/1up | title=Cumana launch 16-bit processor | work=Acorn User | date=November 1985 | accessdate=3 December 2020 | page=9 }}</ref> although subsequent recommended retail prices were around £800 for the upgrade board alone, with "particularly keenly priced" bundles of the board with 10&nbsp;MB and 20&nbsp;MB hard drives available for £900 and £1,000 respectively. Performance concerns associated with the 68008, due to experiences with the [[Sinclair QL]], were alleviated through the presence of "plenty of sub processors", these utilised for managing peripherals including control of floppy and [[Shugart Associates System Interface|SASI]]-compatible hard drives, coupled with the use of a relatively fast 8&nbsp;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&nbsp;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.<ref name="abcomputing198701_cumana">{{ cite magazine | title=Up, Up & Upgrade? | magazine=A&B Computing | last1=Grace | first1=Clive | date=January 1987 | pages=12–16 }}</ref>

Cambridge Microprocessor Systems (CMS) and Control Universal both offered [[Motorola 6809|6809]] second processor solutions equipped with 64&nbsp;KB of RAM and supporting the [[FLEX (operating system)|FLEX]] operating system. The CMS product was a single board that could be fitted inside the BBC Micro's case and connected to the Tube interface internally, with the option of connecting the board externally in a [[Eurocard (printed circuit board)|Eurocard]] rack, whereas Control Universal's product consisted of two separate boards providing the CPU and memory mounted in a Eurocard rack, plus a separate interface board.<ref name="abcomputing1985">{{ cite news | url=https://archive.org/details/AAndBComputing1985Scan/page/n83/mode/2up | title=Flexible Options | work=A&B Computing | date=July 1985 | accessdate=3 December 2020 | last1=Grace | first1=Clive | pages=109–112 }}</ref> Both products employed two [[MOS Technology 6522|6522 VIA]] devices to interface with the Tube interface instead of using a dedicated Tube ULA.<ref name="acornuser198503_6809">{{ cite magazine | url=https://archive.org/details/AcornUser032-Mar85/page/n180/mode/1up | title=6809 A Useful Number | magazine=Acorn User | last1=Fojut | first1=Vincent | date=March 1985 | access-date=10 June 2023 | pages=175, 177, 179 }}</ref> A 6809 second processor project had been pursued internally within Acorn,<ref name="mdfs_toal_6809">{{ cite web | url=https://mdfs.net/Software/Tube/6809/Toal/ | title=Graham Toal's 6809 Second Processor | website=mdfs.net | date=31 October 2007 | access-date=3 October 2021 }}</ref> leading to a tentative product that would offer better support for [[high-level language]]s,<ref name="toal2003a">{{ cite mailing list | url=https://mdfs.net/Software/Tube/6809/Toal/CoPro1.htm | title=Acorn (Was Re: Reading PDP-8 paper tapes) | last=Toal | first=Graham | mailing-list=cctalk | date=1 July 2003 | access-date=3 October 2021 }}</ref> 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.<ref name="toal2003b">{{ cite mailing list | url=https://mdfs.net/Software/Tube/6809/Toal/CoPro2.htm | title=BBC Micro 6809 2nd proc | last=Toal | first=Graham | mailing-list=cctalk | date=1 September 2003 | access-date=3 October 2021 }}</ref>

Permanent Memory Systems produced a 6502 second processor, the B2P 6502, employing a 2&nbsp;MHz [[65C02]] processor{{snd}} as opposed to the faster 6502 device used by the Acorn 6502 Second Processor unit{{snd}} together with 64&nbsp;KB of RAM. Connecting to the Tube and 1&nbsp;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.<ref name="acornuser198703a">{{ cite news | url=https://archive.org/details/AcornUser056-Mar87/page/n146/mode/1up | title=Second Half | work=Acorn User | date=March 1987 | accessdate=3 December 2020 | last1=Rietti | first1=Benjamin | page=145 }}</ref>

==Adapters==
The adapters connected to the BBC Micro's 1&nbsp;MHz bus interface. Adapters could be [[Daisy chain (electrical engineering)|daisy-chain]]ed, allowing more than one to be fitted.

===Teletext adapter===
[[File:BBC Micro and Teletext Adaptor.jpg|thumb|right|alt=The Teletext adaptor has the same style case as the BBC|The BBC with Teletext Adaptor on the right.]]
The [[teletext]]-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]] free over [[Ceefax]]. The hardware and software design was created by Graham Toal.<ref>{{cite web|url=http://mdfs.net/Software/Tube/6809/Toal/CoPro1.htm|title=Acorn (Was Re: Reading PDP-8 paper tapes)|website=mdfs.net}}</ref>  The initial software to use the adapter was quite basic but the BBC decided to rewrite it{{citation needed|date=November 2022|reason=This may be the case, but some background on this decision would be helpful.}} 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.<ref name="abcomputing198810_ontheair">{{ cite magazine | title=On The Air | magazine=A&B Computing | last1=Owen | first1=Ann | date=October 1988 | pages=44–45 }}</ref>

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 [[Belling-Lee connector|75&nbsp;ohm TV aerial]] (in) connector. The adapter contained four manual tuning wheels to receive signals from four different broadcast channels. [http://www.retro-kit.co.uk/user/custom/Acorn/8bit/peripherals/AcornTeletextAdapter/AcornTeletextAdapterRear.jpg Rear view of the adapter].{{citation needed|date=November 2022}} Once tuned, use of the adapter, including switching channels, was controlled via the computer. Teletext pages were displayed on the computer monitor.<ref name="abcomputing198810_ontheair"/>

===Prestel adapter===
The [[Prestel]] adapter was essentially a [[modem]] fitted into the "cheese wedge"-shaped case. It enabled the user to connect to Prestel [[viewdata]] services over a telephone line.

===IEEE 488 interface===
Allowed the BBC Micro to talk over an [[IEEE-488]] bus to specialised equipment. "Acorn" rather than "BBC" branded.

==Econet bridge==
Used to connect two [[Econet]] segments together. An Econet bridge is capable of automatically learning a simple [[network topology]] and selectively forwarding [[network packet|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==
<references/>

==External links==
===General===
*[https://web.archive.org/web/20070128192453/http://www.beebmaster.co.uk/MyCheeseWedges.html BeebMaster's Cheese Wedges]
*[http://chrisacorns.computinghistory.org.uk/8bit_Upgrades/Acorn_ANC01_65022ndproc.html Chris' Acorns]

===32016===
*[http://www.binarydinosaurs.co.uk/Museum/Acorn/32016copro/index.php Binary Dinosaurs 32016 co-processor]
*[https://web.archive.org/web/20070128192534/http://www.beebmaster.co.uk/Cambridge2.html BeebMaster's 32016]
*[http://www.computinghistory.org.uk/cgi-bin/sitewise.pl?act=det&p=4606 Acorn Cambridge Co-Processor @ The Centre for Computing History]

===Acorn Cambridge Workstation===
*[http://chrisacorns.computinghistory.org.uk/Computers/ABC.html Acorn Business Computer]

===ARM Evaluation System===
*[http://www.heyrick.co.uk/assembler/proctype.html ARM Processor types]
*[http://www.stumpie.com/armeval/ ARM Evaluation System pictures]
*[https://web.archive.org/web/20081010152248/http://www.dunnington.u-net.com/public/BBC/ARMeval.html ARM Evaluation System software]
*[http://www.computinghistory.org.uk/det/4617/Acorn-ARM-Evaluation-System Acorn ARM Evaluation System @ The Centre for Computing History]

{{BBC Computer Literacy Project}}
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{{Use British English|date=January 2025}}

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[[Category:Acorn Computers]]
[[Category:Legacy hardware]]