== Technical ==
Dobbertin HD20 is a relative of the Winchester type hard disk.There is a CPC interface which connects to a PC-XT interface.
It is claimed it is a PC-XT interface with an interface between that and the CPC. The OMTI 5510 appears to be very closein terms of operation and commands, but the Dobbertin is probably not this. The command descriptions and operation appear to be the same although the software seems to only use TEST READY, READ, WRITE, SEEK (parking), SET PARAMETERS and FORMAT.
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:
#FBE0 Dobbertin Harddisc Data Port(read/write) #FBE1 Dobbertin Harddisc Status(read), Reset(write) #FBE2 Dobbertin Harddisc Select(write), Configuration(read)
#FBE3 Dobbertin Harddisc DMA, Interrupt (Used on CPC???)
#FBE4 Dobbertin Harddisc Reset(read or write will reset) (Exact port decodings to be confirmed; the GALs probably describe it)
The hard drive interface is an PC-XT compatible hard disc interface. The CPC's port mappings are close to the PC-XT's port mappings.