[[Image:Dobbertin.gif|thumb|Dobbertin Logo]]
A harddisc manufactured by the German company [[Dobbertin|Dobbertin Industrie-Elektronik]].
One of the first ways to connect a Harddisc to the CPC.
*[[Cosmos]]
*Dobbertin CP/M 2.2 (63 KB TPA) and CP/M Plus
*[[FutureOS|FutureOS]] using all four partitions (I, J, K and L)
*[[Maxam_2|MAXAM II]]
*[[Prowort]] via using Dobbertin CP/M Plus (partitions D, E, F and G)
*[[X-DDOS|X-DDOS]] (v2.10)
*[[Z3Plus]] and [[NZ-COM]](providing hundreds of additional applications)*'-HD20BackUp' to backup / compare / restore the complete 20 MB hard disc* In addition a lot of (cracked) games are able to run from the HD-20 hard disc
== Technical ==
There is an expansion port interface which connects to the CPC.
It contains a 16KB ROM containing XD[[X-DOS DDOS]] which is normally in slot 6 but can be configured between 1 and 7.
There is a CPC interface which connects to a PC-XT interface.
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 [[XDX-DOSDDOS]] v2.10 (which supports the harddisc20 MB hard-disc, and additionally supports external double sided 80 track disc drives).
The 20 MB harddisc hard-disc 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. They can be accessed at the same time, so all 20 MB are usable at the same time.
#FBE2 Dobbertin Harddisc Select (write), Configuration (read)
#FBE3 Dobbertin Harddisc DMA, Interrupt (Used on CPC???)
#FBE4 -FBE7 Dobbertin Harddisc Reset (read or write will reset)
(Exact Port decoding: A15-A10, A8-A7 are decoded by U11. A4,A3 from U9B. A9 is G1, A2 = A, A5 = B, A6 = C into U10 A1,A0 are used when I/O range FBE0-FBE3. R/W are used. Data is used by device. FBE0-FBE3 are decoded as 111110111110000rr R/W not used, so read and write will access this port decodings to be confirmed; . Data is not important. FBE4 is decoded as 111110111110001xx Therefore FBE4-FBE7 access the GALs probably describe it)same port. There is additional port decoding which appears to force bus value with some I/O reads, interrupt request, rom read and ram read. The purpose is not clear.
The hard drive interface is an PC-XT compatible hard disc interface.
These are real hardware values!
== Emulation ==
The Dobbertin HD20 is emulated by the Symbiface III since 7/2023. Therefore you need a subfolder 'HD20' on the USB stick. It needs to contain the 21 MB hard-disc image file.
It is also [https://www.cpcwiki.eu/forum/emulators/got-bored-again/ emulated in MAME since 6/2015]
== Other harddisc solutions for the CPC ==
Modern:
* [[Albireo]] (SD card)
* [[CPC-IDE]] (IDE)
* [[HDCPC]] (IDE)
* [[IDE8255]] (IDE)
* [[M4 Board]] (SD card)
* [[SYMBiFACE II]] (IDE)
* [[SYMBiFACE III]] (USB, SD card)
* [[X-MASS]] (IDE)
* support for CP/M 2.2 with 63K TPA (requires 128 KB RAM), and for CP/M Plus
* support for Softwareclock and TIMEROM+ (Real Time Clock under CP/M Plus)
* Price: DM 1100.-(approx. 562 Euros)
== Promo (German) ==
== Links ==
* ftp://ftp.seagate.com/techsuppt/controllers/st11m-r.txt
* http://hardware.speccy.org/temp/Amstrad-DiscoDuro.html
* http://heathkit.garlanger.com/companies/ShugartAssociates/sasi_r0a.pdf