(The Plus 3 had been rumoured to offer Acorn's DFS and to feature a 8272 double-density disk controller before its launch.) Because the WD1770 is capable of single-density mode and uses the same IBM360-derived floppy disc format as the Intel 8271 found in the BBC Micro, it was also possible to use the Disc Filing System with an alternate ROM, such as the ACP 1770 DFS. The Plus 3 reset PAGE to &1D00, reducing the amount of free RAM available to the user.
A 20 MB hard drive was offered at a price of £805. ====Advanced Plus 4==== Announced in early 1986, the Advanced Plus 4 (AP4) from Advanced Computer Products was a cartridge-based interface employing the WD1770 controller and featuring ACP's 1770 DFS product, providing compatibility with Acorn's DFS from the BBC Micro and thereby supporting seven-character filenames and up to 31 files per disc.
An extra ROM socket was provided for a user-fitted sideways ROM, and being a 1770-based interface, it was reported that Acorn's ADFS could be used instead, although since it was not aware of the additional RAM, PAGE would be raised to &1D00 as it would be when using Acorn's Plus 3.
Reports during the second half of 1982 indicated a potential December release, with Curry providing qualified confirmation of such plans, together with an accurate depiction of the machine's form and capabilities, noting that the "massive ULA" would be the "dominant factor" in any pre-Christmas release.
The Acorn Electron is a budget version of the BBC Micro educational/[computer] introduced by Acorn Computers Ltd on 25 August 1983.
However, as the end of the year approached, with the ULA not ready for "main production", the launch of the Electron was to be delayed until the spring. By June 1983, with the planned March release having passed, the launch of the Electron had been rescheduled for the Acorn User Exhibition in August 1983, and the machine was indeed launched at the event with a new price of £199.
By October 1983, Acorn had received orders for more than 150,000 units, but had production targets of only 25,000 a month before Christmas, meaning that the existing backlog would take more than six months to fulfil.
Hohenberg later noted that after the 1983 Christmas season, Electron deliveries had increased to meet a demand that was no longer there, with the market having "completely dried up".
The company expected to ship the Electron before Christmas, and sell 100,000 by February 1984.
Acorn's marketing manager, Tom Hohenberg, admitted in early 1984 that "a lot of the trouble stemmed from the ULA" in getting production to the desired levels, but that such difficulties had been resolved, although Acorn faced an order backlog of almost a quarter of a million units. As the company increased production during 1984, however, the British home computer market greatly weakened.
Acorn's Christmas 1984 sales were greatly below expectations and by March 1985 the company had reduced the Electron's price to £129.
Support for the E00 ADFS offered by PRES for that company's AP3 disc system was indicated as an application for the sideways RAM. ===Disc interfaces=== The first disc interface to be announced for the Electron was Pace's Le Box in 1984, offering a single-sided 100 KB floppy drive controlled by the 8271 controller and accessed using the Amcom Disc Filing System, with pricing at £299 plus VAT including the drive or around £199 without.
Morley Electronics instead chose to offer an expansion combining the display and reception capabilities. ====Sir Computers==== In late 1984, Sir Computers announced a Mode 7 adapter unit that plugged into the Electron's expansion connector.
Acorn's Christmas 1984 sales were greatly below expectations and by March 1985 the company had reduced the Electron's price to £129.
Various board upgrade options were also offered between the variants, with the product being described mainly as a vehicle to expose the bundled software packages to as many as 150,000 owners of the estimated 200,000 Electrons in the UK who "have not yet been able to acquire or use View or Viewsheet". ===Communications and networking=== To support connectivity, Acorn announced a Plus 2 network interface with availability scheduled for early 1985, together with a RS423 cartridge for the Plus 1.
However, an Econet interface was produced by Barson Computers in Australia and possibly other individuals and businesses. ====Acorn Plus 4==== The Acorn Plus 4 interface was due to provide a modem communications capability. ====Andyk RS423 cartridge==== Andyk announced an RS423 cartridge for the Plus 1 providing a serial port, alongside other products, in late 1985.
This meant that the storage capacity of each disc was increased from the 320 KB of the original Plus 3 to 640 KB (this being supported by ADFS on the Master Compact). ====Cumana Floppy Disc System==== Early in 1985, Cumana released a cartridge-based interface providing support for double-density storage, a real-time clock and calendar for timestamping of files, and a spare ROM socket for user-fitted sideways ROMs.
Advanced Plus 5 and Acorn 6502 2nd Processor. ===Sound system expansions=== Despite the Electron having only limited sound generation capabilities, few expansions were offered to overcome the machine's limitations. ====Millsgrade Voxbox==== Advertised in late 1985, the Voxbox by Millsgrade Limited was an expansion connecting to the Electron's expansion connector that provided allophone-based speech synthesis, with driver software provided on cassette.
Acorn committed to supporting the machine "until the end of 1986", continuing to supply it (as the Merlin M2105) to British Telecom as part of the Healthnet communications system, with small-scale manufacturing continuing while existing stocks were being run down. By autumn, retailers appeared eager to discount the computer, with prices in stores as low as £100, reportedly less than the distributor prices of the summer months.
A 20 MB hard drive was offered at a price of £805. ====Advanced Plus 4==== Announced in early 1986, the Advanced Plus 4 (AP4) from Advanced Computer Products was a cartridge-based interface employing the WD1770 controller and featuring ACP's 1770 DFS product, providing compatibility with Acorn's DFS from the BBC Micro and thereby supporting seven-character filenames and up to 31 files per disc.
The precise DFS variant used by the Pegasus 400 system introduced "typeahead" support permitting keystroke buffering during disc activity on systems with the Turbo-Driver or Master RAM Board fitted and enabled. ===Slogger/Elektuur Turbo boards=== Announced in early 1986, the Slogger Turbo-Driver was a professionally fitted upgrade priced at £42.
The price of the unit in late 1986 was £66.70. The additional facilities of the AP5 alongside the Tube interface permitted various expansions for the BBC Micro to be made available for the Electron.
These included the Hybrid Music 5000 and the AMX Mouse. ====PMS Electron Second Processor==== In 1986, Permanent Memory Systems announced a second processor product for the Electron, the PMS-E2P, as a self-contained cartridge for use with the Plus 1 containing a second 2 MHz 6502A processor plus 64 KB of RAM, priced at £89.
Announced in late 1987, the product was made possible by an agreement between ACP and Acorn to license the ADFS software.
The SEDFS ROM was also available separately for existing Cumana interface owners, priced at £24.95. The SEDFS was later bundled with Slogger's own cartridge-based interface and a 40/80-track switchable drive offering up to 400 KB storage per disc, with the bundle taking the Pegasus 400 name, introduced as part of a sales tour towards the end of 1987.
Unfortunately, Sir Computers ceased trading before the product was brought to market. ====Jafa Systems==== Released in 1987 at a price of £89, the Mode 7 Mark 1 Display Unit was a separate unit "about the size, shape and colour of the Plus One or a Slogger ROMbox" that connected to the Electron's expansion connector and featured a Motorola 6845 display controller and Mullard SAA5050 character generator to replicate the main elements of the BBC Micro's Teletext display solution.
It also used up 20 KB of RAM for the graphics display rather than the 1000 bytes of a hardware Mode 7. A conceptually similar predecessor to the software-based simulator was published by Electron User in early 1987, offering a monochrome Mode 4 simulation of the Teletext display, using the lower 25 character lines of the screen to show the Teletext output, reserving several lines at the top of the screen for a representation of Mode 7 used to prepare the eventual visual output.
The expansion used the General Instrument SP0256A-AL2 speech synthesis chip. ====Sound Expansion cartridge==== Originally announced in 1987 by Project Expansions to be priced at around £40, the Sound Expansion cartridge could be fitted in a Plus 1 (or compatible) slot and provide sound output equivalent to that of the BBC Micro, with Superior Software's Speech bundled as a "limited offer".
To support the output of both the Mode 7 display and the existing video output, a lead connected the Electron's RGB output to the expansion, with the expansion providing only RF (television) output. Conscious of the relatively high price of the Mark 1 unit, John Wike of Jafa devised and, at the end of 1988, introduced a software-based Mode 7 Simulator, priced at £25, supplied on a ROM cartridge that rendered the Mode 7 display in a low-resolution, 8-colour graphics mode.
The ROM image was supplied on disc for £17.19, whereas a bundle of the ROM and ABR cartridge was £50.95. In 1989, the Advanced Plus 3 Mark 2 was launched, offering a double-sided drive in place of the single-sided drive previously offered.
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