Looks like I'm coming up empty handed with my requests for the missing Systemhandbuch frown
In the mean time I've looked at small system utilities that might tell someone versed in x86 code where they want to access hardware:

- crt.com switches between alpha and graphics mode and changes the bit-image-print-flag (whatever that is)
- hdinit.com is the harddisk formatter
- klickon/klickoff.com toggles the rather annoying keyboard klick from the beeper in the keyboard
- negativ/positiv.com toggles the screen between black on white and white on black letters
- video.com sets or cancels a screen saver (video time-out)
- set48tpi.com sets double stepping for the 96tpi drives

https://dl.dropboxusercontent.com/u/55419307/Siemens%20PC-D/PCD%20Utilities.rar


NCR DMV- DEC Rainbow- Siemens PCD- ITT 3030-Oly People- Acorn A5000- Olivetti M20