Dobbertin HD20 is a hard disk that has an interface that appears to implement the SASI protocol (Shugart Associates System Interface) (a precursor to the SCSI) but which has registers which look similar to those of the OMTI 5510. (The SASI protocol is also used by the SA1000). The controller is a Seagate ST-11M.
There is an expansion port interface which connects to the CPC. It contains a 16KB ROM containing XD-DOS which is normally in slot 6but can be configured between 1 and 15.
There is a CPC interface which connects to a PC-XT interface.
The disc format appears to be CPM/AMSDOS based, with 0x0e5 as the format data byte.
* 512 bytes per sector (possibly defined with jumpers)
* 17 sectors per cylinder (possibly defined with jumpers)
* &e5 format filler byte
* 4 heads (configured by xd-dos)
* 614 cylinders (configured by xd-dos)
== Other harddisc solutions for the CPC ==