Editing Acorn Electron (section)

===Disc interfaces===
The first disc interface to be announced for the Electron was Pace's Le Box in 1984, offering a single-sided 100&nbsp;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. The unit also provided eight sideways ROM sockets and was intended to sit under the Electron itself.<ref name="acornuser198409">{{ cite magazine | url=https://archive.org/details/AcornUser026-Sep84/page/n11/mode/1up | title=Pace first with drive link for Electron | magazine=Acorn User | date=September 1984 | access-date=13 January 2021 | page=10 }}</ref> The unit was connected via cabling to the expansion edge connector and included its own power supply, and other drives including switchable 40/80 track drives offering up to 400&nbsp;KB capacity were dealer-supplied options.<ref name="electronuser198410a">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume2/Electron-User-02-01/page/n6/mode/1up | title=Le Box puts discs on tap | magazine=Electron User | date=October 1984 | access-date=13 January 2021 | page=7 }}</ref> Although the product was meant to be on sale at the Acorn User Show in August 1984,<ref name="acornuser198409" /> and had been advertised,<ref name="electronuser198409">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume1/Electron_User_01-12/page/n48/mode/1up | title=Le Box Electron Disc Interface | magazine=Electron User | date=September 1984 | access-date=14 January 2021 | page=49 }}</ref> it was "discontinued" in early 1985 before getting to market, with a Pace representative indicating that prohibitive pricing of the 8271 chips (each at "over £80 at times") had left the company considering a re-launch of the product should the pricing situation become more favourable.<ref name="acornuser198503">{{ cite magazine | url=https://archive.org/details/AcornUser032-Mar85/page/n10/mode/1up | title=New DFS in Plus 3 add-on for Electron | magazine=Acorn User | date=March 1985 | access-date=13 January 2021 | page=9 }}</ref>

Following on from Acorn's Plus 3 interface, [[Cumana (company)|Cumana]], Solidisk, Advanced Computer Products and Slogger all offered disc interfaces for the Electron. Unlike disc systems on the BBC Micro and the Acorn Plus 3, many of the systems released for the Electron did not claim RAM workspace (and raise the PAGE variable affecting applications above the default of &E00), making it easier to use cassette-based software transferred to disc and to run larger programs from disc.<ref name="electronuser198605c">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume3/Electron-User-03-08/page/n6/mode/1up | title=School plumps for mobile Electrons | magazine=Electron User | volume=3 | issue=8 | date=May 1986 | access-date=17 January 2021 | page=7 | quote="With PAGE the same as the tape system{{snd}} unlike the BBC DFS{{snd}} tape to disc transfer is easy..." }}</ref>

Low-cost alternatives to disc systems, briefly made fashionable by press coverage of the [[ZX Microdrive|Sinclair Microdrive]], were reportedly under development by expansion suppliers such as Solidisk,<ref name="electronuser198402gpi"/> and finished products such as the Phloopy [[Endless tape cartridge|looped tape]] system were offered for the Electron.<ref name="electronuser198501_phloopy">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume2/Electron-User-02-04/page/n5/mode/1up | title=Phloopy speeds the load | magazine=Electron User | date=January 1985 | access-date=13 February 2023 | pages=6 }}</ref> Reliability issues were described with the Phloopy, and the product was apparently short-lived.<ref name="electronuser199001_timewarp">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume7/Electron-User-07-04/page/n18/mode/1up | title=Time Warp 1985 | magazine=Electron User | last1=Woods | first1=Barry | date=January 1990 | access-date=13 February 2023 | pages=19 }}</ref>

====Acorn Plus 3====
[[File:Acorn ALA13 Electron Plus 3 (front).jpg|thumb|Acorn Plus 3, showing the connector and disc drive]]
Launched in late 1984 for a price of £229,<ref name="popcompweekly19841122">{{ cite news | url=https://archive.org/details/popular-computing-weekly-1984-11-22/page/n4/mode/1up | title=New Acorn products at Compec | work=Popular Computing Weekly | date=22 November 1984 | access-date=28 December 2020 | page=5 }}</ref> the Acorn Plus 3 was a hardware module that connected independently of the Plus 1 and provided a "self contained disc interface and 3.5 inch single sided disc drive" offering over 300&nbsp;KB of storage per disc using the newly introduced [[Advanced Disc Filing System]] (ADFS).<ref name="plus3">{{ cite book | url=http://www.4corn.co.uk/archive/docs/AMPAPP/150/AMP056%20-%20Electron%20Plus%203-opt.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.4corn.co.uk/archive/docs/AMPAPP/150/AMP056%20-%20Electron%20Plus%203-opt.pdf |archive-date=2022-10-09 |url-status=live | title=Electron Plus 3: New dimensions in capability | publisher=Acorn Computers Limited | page=2 }}</ref> The Plus 3 was also reportedly produced with a double-sided drive fitted.<ref name="electronuser198503_plus3">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume2/Electron-User-02-06/page/n34/mode/1up | title=...and then there was Plus 3 | magazine=Electron User | date=March 1985 | volume=2 | issue=6 | access-date=6 March 2021 | last1=Peters | first1=Nigel | page=35 | quote=Some versions of the Plus 3 allow both sides of the disc to be used, allowing 640k of information to be stored. }}</ref>

An expansion connector for a second 3.5- or 5.25-inch drive was also provided by the unit, with such drives needing to provide a [[Shugart bus|Shugart]]-compatible connector and their own power supply.<ref name="plus3ug">{{ cite book | url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/Manuals/Acorn_Plus3UG.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://chrisacorns.computinghistory.org.uk/docs/Acorn/Manuals/Acorn_Plus3UG.pdf |archive-date=2022-10-09 |url-status=live | title=The Electron Plus 3 User Guide | publisher=Acorn Computers Limited | date=October 1984 | issue=1 | access-date=6 March 2021 }}</ref>{{rp|page=4}} The original Electron edge connector was repeated on the back of the Plus 3, allowing the Plus 1 or other compatible expansion to be connected in conjunction with the Plus 3.<ref name="plus3ug" />{{rp|page=5}}

The double-density drive of the Plus 3 was driven using a [[WD1770]] drive controller by the ADFS. (The Plus 3 had been rumoured to offer Acorn's DFS and to feature an 8272 double-density [[disk controller]] before its launch.<ref name="electronuser198411">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume2/Electron-User-02-02/page/n4/mode/1up | title=Electron disc drive - and it's official | magazine=Electron User | date=November 1984 | access-date=13 January 2021 | page=5 }}</ref>) 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.<ref name="electronuser198602_acp1770dfs">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume3/Electron-User-03-05/page/n53/mode/1up | title=ROMs | magazine=Electron User | date=February 1986 | volume=3 | issue=5 | access-date=6 March 2021 | last1=Waddilove | first1=Roland | page=54 }}</ref>

The Plus 3 reset PAGE to &1D00, reducing the amount of free RAM available to the user.<ref name="plus3ug" />{{rp|page=52}} The ADFS system could be temporarily disabled (and PAGE reset to &E00) via the {{kbd|*NOADFS}} command.<ref name="plus3ug" />{{rp|page=15}} Later products such as the PRES E00 ADFS remedied the memory demands of the ADFS, along with other issues suffered by the software as delivered with the Plus 3.<ref name="electronuser198808" /> If using the Plus 3 in screen modes 0–3, the pseudo-variable {{mono|TIME}} would be thrown off, as the interrupts were disabled during disk access in these modes. The screen would also blank during disc accesses.<ref name="plus3ug" />{{rp|pages=14–15}}

Disks had to be manually [[Mount (computing)|mounted]] and dismounted using the {{kbd|*MOUNT}} / {{kbd|*DISMOUNT}} commands, or using the {{keypress|Ctrl}}+{{keypress|A}}+{{keypress|Break}} key combination. Disks could also be booted from via the standard {{keypress|Shift}}+{{keypress|Break}} key-combination, if the !BOOT file was present on the disk. This behaviour was the same as on the BBC Micro.<ref name="plus3ug" />{{rp|page=18}}

The Plus 3 included an uprated square black power supply unit with mains cord, manufactured by STC, designed and manufactured in England to {{nowrap|[[British Standards|BS]] 415}} and {{nowrap|BS 5850}}, that was designed to power the Plus 3, in addition to the Electron and the Plus 1 interface as well.<ref name="acorn_mains_adaptor">{{cite web | url=http://www.stardot.org.uk/forums/download/file.php?id=4417 | title=Plus 3 Disc Unit Mains Adaptor (36 watts) | date=4 October 1984 | issue=2 | access-date=14 March 2021 }}</ref> This replaced the original cream-coloured "wall wart" style power supply, designed to {{nowrap|BS 415}} and manufactured in Hong Kong.

* '''Original''' Part no: 0201,113;<ref name="acorn_do_0201">{{ cite tech report | url=http://www.4corn.co.uk/archive/do/registers/x201/0201.txt | title=0201 DETAIL DRAWINGS | publisher=Acorn Computers Limited | access-date=14 March 2021 }}</ref> input 220/240 V AC/50&nbsp;Hz; output 19 V AC/0.737 A/14 W:  '''Usage''': Electron, Electron+Plus1
* '''Uprated''' Part no: 0865,010; input 240&nbsp;V AC/50&nbsp;Hz 50&nbsp;W; output 21&nbsp;V AC/1.75&nbsp;A/36.75&nbsp;W: '''Usage''': Electron+Plus3, Electron+Plus3+Plus1

Repair note: If the internal power-supply connector, used to power the existing internal 3.5-inch drive is damaged, and requires replacement, then the original AMP 800-930 4-pin connector, which was already in short supply during the original production run, may be replaced with a Molex 5264 50-37-5043 "Mini-SPOX" connector as an alternative.<ref name="acorn_memo">{{cite tech report | url=http://www.stardot.org.uk/forums/download/file.php?id=4417 | title=Acorn Electron Disc Drive Connector{{snd}} Internal Memo | publisher=Acorn Computers Limited | last1=Ashby | first1=Simon | date=7 September 1984 | access-date=14 March 2021 }}</ref>

====Advanced Plus 3====
[[File:Advanced Plus 3.jpg|thumb|right|250px|The PRES Advanced Plus 3 with a 3½-inch drive]]
Designed and produced by Baildon Electronics and sold by PRES, the Advanced Plus 3 (AP3) was a Plus 1 cartridge interface using the WD1770 controller, supplied with Acorn's ADFS and a single-sided 3½-inch disc drive for £99 plus VAT, offering equivalent functionality to the Acorn Plus 3.<ref name="electronuser198710a">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume5/Electron-User-05-01/page/n3/mode/1up | title=PRES announce Advanced Plus 3 | magazine=Electron User | volume=5 | issue=1 | date=October 1987 | access-date=20 January 2021 | page=4 }}</ref> Announced in late 1987, the product was made possible by an agreement between ACP and Acorn to license the ADFS software.<ref name="electronuser198710b">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume5/Electron-User-05-01/page/n3/mode/1up | title=Plus 3 upgrade | magazine=Electron User | volume=5 | issue=1 | date=October 1987 | access-date=20 January 2021 | page=5 }}</ref> As with many disc interfaces for the Electron, since the interface provided a connector for the drive, this made it possible to connect a 5¼" floppy disc drive (more common amongst BBC Micro owners) or the more typical 3½-inch drive.

PRES later released a version of ADFS with support for PAGE at &E00, this being achieved by using RAM provided by the Advanced Battery Backed RAM (ABR) cartridge. This version also fixed two notable bugs in Acorn's ADFS, eliminating unreliability when accessing the first tracks on a disc which had previously necessitated the writing of a file (ZYSYSHELP) as a workaround, and switching off the text cursor during disc compaction which had previously caused disc corruption (since the disc data would be processed using screen memory during this operation, and the cursor would modify that data when blinking). The ROM image was supplied on disc for £17.19, whereas a bundle of the ROM image and ABR cartridge was £50.95.<ref name="electronuser198808">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume5/Electron-User-05-11/page/n8/mode/1up | title=Improving on perfection | magazine=Electron User | volume=5 | issue=11 | date=August 1988 | access-date=20 January 2021 | last1=Waddilove | first1=Roland | page=9 }}</ref> A separate ADFS version 1.1 product, offered as a 16&nbsp;KB ROM, also provided these bug fixes. Advertised slightly earlier than the E00 ADFS,<ref name="electronuser198712_pres">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume5/Electron-User-05-03/page/n3/mode/1up | title=New Product ADFS E00 | magazine=Electron User | date=December 1987 | access-date=14 May 2025 | pages=4 }}</ref> it also replaced the Winchester hard drive support traditionally found in ADFS with "'patches' for future enhancements".<ref name="electronuser198711_pres">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume5/Electron-User-05-02/page/n3/mode/1up | title=New Product ADFS Version 1.1 for the Electron | magazine=Electron User | date=November 1987 | access-date=14 May 2025 | pages=4 }}</ref> Such patches, present in both of these ADFS variants, amounted to support for a 256&nbsp;KB RAM disc provided by the company's Advanced Quarter Meg RAM cartridge.<ref name="electronuser198807_pres">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume5/Electron-User-05-10/page/n33/mode/2up | title=PRES | magazine=Electron User | date=July 1988 | access-date=15 May 2025 | pages=34–35 }}</ref>

In 1989, the Advanced Plus 3 Mark 2 was launched, offering a double-sided drive in place of the single-sided drive previously offered. This meant that the storage capacity of each disc was increased from the 320&nbsp;KB of the original Plus 3 to 640&nbsp;KB (this being supported by ADFS on the Master Compact).<ref name="electronuser198905ap3">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume6/Electron-User-06-08/page/n4/mode/1up | title=It's the Plus 3+ | magazine=Electron User | volume=6 | issue=8 | date=May 1989 | access-date=21 January 2021 | page=5 }}</ref>

====Cumana Floppy Disc System====
Early in 1985,<ref name="electronuser198502">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume2/Electron-User-02-05/page/n5/mode/1up | title=Disc drive battle is joined | magazine=Electron User | date=February 1985 | access-date=13 January 2021 | page=6 }}</ref> 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.<ref name="cumana_disc_interface">{{ cite book | url=http://www.4corn.co.uk/archive/showpdfs/04%20Micro%20User-Electron%20User%20May%201985%20-%20Westminster/Cumana%20-%20electron%20disk%20drive%20interface.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.4corn.co.uk/archive/showpdfs/04%20Micro%20User-Electron%20User%20May%201985%20-%20Westminster/Cumana%20-%20electron%20disk%20drive%20interface.pdf |archive-date=2022-10-09 |url-status=live | title=Acorn Electron - Disc Drive Interface | publisher=Cumana Limited | date=March 1985 | access-date=21 March 2021 }}</ref> The filing system used was Cumana's own QFS, supporting 89 files per disc,<ref name="electronuser198507a">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume2/Electron-User-02-10/page/n44/mode/1up | title=It's great being two-faced and twice as dense | magazine=Electron User | date=July 1985 | access-date=13 January 2021 | page=45 }}</ref> PAGE at &E00,<ref name="electronuser198605c" /> a non-hierarchical catalogue, ten-character filenames, with a format not directly compatible with either of Acorn's DFS or ADFS.<ref name="electronuser198507">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume2/Electron-User-02-10/page/n27/mode/1up | title=The Cumana floppy disc system for the Electron: It's an impressive piece of work | magazine=Electron User | date=July 1985 | access-date=13 January 2021 | last1=Peters | first1=Nigel | page=28 }}</ref> The interface itself cost £149.95 when originally announced,<ref name="electronuser198502" /> but settled at around £115.95 including VAT, also being offered in a promotional bundle with a 5¼-inch drive for £224.15 including VAT.<ref name="electronuser198507b">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume2/Electron-User-02-10/page/n51/mode/1up | title=Disc power at a new low price! | magazine=Electron User | date=July 1985 | access-date=13 January 2021 | page=52 }}</ref> Later pricing put the interface at £74.95 including VAT.<ref name="electronuser198601">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume3/Electron-User-03-04/page/n9/mode/1up | title=Electron Double Density Disk Interface Super Saver | magazine=Electron User | volume=3 | issue=4 | date=January 1986 | access-date=17 January 2021 | page=10 }}</ref>

====Solidisk EFS====
In mid-1985, Solidisk released a cartridge-based interface with support for single and double density storage and providing Acorn DFS and ADFS compatibility, 16&nbsp;KB of on-board sideways RAM, and a connector for a Winchester hard drive. The cartridge itself cost £59, with a bundle including a double-sided, double-density, 3½-inch drive costing £200.<ref name="electronuser198508">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume2/Electron-User-02-11/page/n5/mode/1up | title=Add-on for the Plus 1 | magazine=Electron User | date=August 1985 | access-date=13 January 2021 | page=6 }}</ref> A 20&nbsp;MB hard drive was offered at a price of £805. PAGE was set to &1900 when using the Solidisk system.<ref name="electronuser198508a">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume2/Electron-User-02-11/page/n8/mode/2up | title=Solidisk EFS combines disc upgrade, 16K sideways RAM and a socket for the Winchester for only £59.00 | magazine=Electron User | date=August 1985 | access-date=13 January 2021 | pages=8–9 }}</ref>

====Advanced Plus 4====
Announced in early 1986,<ref name="electronuser198603ap4">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume3/Electron-User-03-06/page/n4/mode/1up | title=Interface opens up software range for Electron | magazine=Electron User | volume=3 | issue=6 | date=March 1986 | access-date=17 January 2021 | page=5 }}</ref> 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. However, 8&nbsp;KB of on-board static RAM was used as workspace for the filing system, keeping PAGE at &E00. 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. The interface was priced at £69.55 plus VAT.<ref name="electronuser198606a">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume3/Electron-User-03-09/page/n18/mode/1up | title=Disc drive compatibility at long last | magazine=Electron User | volume=3 | issue=9 | date=June 1986 | access-date=17 January 2021 | page=19 }}</ref>

====Slogger Electron Disc System and Pegasus 400====
Slogger, an established producer of expansions and a reseller of other disc systems, introduced the Electron Disc System in early 1987, priced at £74.95, featuring the Cumana Floppy Disc System interface,<ref name="electronuser198704a">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume4/Electron-User-04-07/page/n13/mode/1up | title=New Release | magazine=Electron User | volume=4 | issue=7 | date=April 1987 | access-date=18 January 2021 | page=74 }}</ref> which was combined with an Acorn-compatible DFS, SEDFS, having the capability of reading 40-track discs on 80-track drives plus support for Slogger's tape-to-disc conversion products,<ref name="electronuser198704">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume4/Electron-User-04-07/page/n4/mode/1up | title=Disc power gives Electron a boost | magazine=Electron User | volume=4 | issue=7 | date=April 1987 | access-date=18 January 2021 | page=5 }}</ref> and reported as offering "virtual 100 per cent 8271 emulation" for compatibility with traditional DFS software.<ref name="electronuser198706">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume4/Electron-User-04-09/page/n55/mode/2up | title=DFS upgrade with BBC {{sic|compata|bility|nolink=y}} | magazine=Electron User | volume=5 | issue=9 | date=June 1987 | access-date=19 January 2021 | last1=Smiddy | first1=Mark | pages=56–57 }}</ref> The SEDFS ROM was also available separately for existing Cumana interface owners, priced at £24.95.<ref name="electronuser198704a" />

The SEDFS was later bundled with Slogger's own cartridge-based interface and a 40/80-track switchable drive offering up to 400&nbsp;KB storage per disc, with the bundle taking the Pegasus 400 name, introduced as part of a sales tour towards the end of 1987. This package of interface and drive cost £130.<ref name="electronuser198712">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume5/Electron-User-05-03/page/n5/mode/1up | title=Slogging around the country | magazine=Electron User | volume=5 | issue=3 | date=December 1987 | access-date=18 January 2021 | page=6 }}</ref> The precise DFS variant used by the Pegasus 400 system kept PAGE at &E00 and introduced "typeahead" support, permitting keystroke buffering during disc activity on systems with the Turbo-Driver or Master RAM Board fitted and enabled.<ref name="electronuser198901">{{ cite magazine | url=https://archive.org/details/ElectronUserVolume6/Electron-User-06-04/page/n24/mode/1up | title=Driving hardware | magazine=Electron User | volume=6 | issue=4 | date=January 1989 | access-date=20 January 2021 | last1=Waddilove | first1=Roland | pages=25–26 }}</ref>