Editing Acorn Electron (section)

====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>