a 5¼-inch drive for £224.15 including VAT. Later pricing put the interface at £74.95 including VAT. 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 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. 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. However, 8 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. 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, 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, and reported as offering "virtual 100 per cent 8271 emulation" for compatibility with traditional DFS 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. This package of interface and drive cost £130. 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