Hello Olympia Boss Fans,
I have good news for emulation of the "high end" Boss D Model:
I have just completed a clean CPM format of the original St506 in a real Boss D.
There is an Option to create two "partitions" - one for CPM and one for Prologue.
This was only possible by using a special Boss D CPM Bootdisk which has the BIOS to access the harddisk.
I will share the files on vzekc.de:https://forum.classic-computing.de/forum/index.php?thread/21284-olympia-boss-d-cpm-harddisk-support/
I am promised to get circuit diagramms as well one day, so stay tuned :-)