== Technical ==
Dobbertin HD20 probably uses a modified pc-xt interface which uses a Winchester type hard disk.The WD1002-SHD datasheet describes a basic set of commands. The status register values are outputs from the chip itself. But here you can find the list of commands, their parameters and results. The other link describes more extensive Winchester commands extending the WD1002. The actual Winchester implementation in the HD20 is not known.
Uses [[XD-DOS]] v2.10 (which supports the harddisc, and additionally supports external double sided 80 track disc drives). The 20 MB harddisc is split into four partitions, with drive names D, E, F, and G (drive name C isn't used here, but may be used as RAM disc, in combination with Dobbertin RAM expansion). Under [[FutureOS]] the four partitions are named I, J, K and L. The hard disc is controlled by this I/O Ports: