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. Advanced Plus 3 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. Announced in late 1987, the product was made possible by an agreement between ACP and Acorn to license the ADFS software. 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 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. 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. The filing system used was Cumana's own QFS, supporting 89 files per disc, PAGE at &E00, a non-hierarchical catalogue, ten-character filenames, with a format not directly compatible with either of Acorn's DFS or ADFS. The interface itself cost £149.95 when originally announced, but settled at around £115.95 including VAT, also being offered in a promotional bundle with