Thanks for the explanation of GO.COM, I am with it now. I have now managed to boot xbeaver without the GM833 card and can see A: and B:. Although I did download the latest version I think I must have mixed up the versions and re-compiled a previous one... Doh!
In order to use gensys.com to create a boot disk for my real Gemini with RPM, I decided to build a bios based on BIOSFW.SYS rather than BIOSW.SYS. As I understand it this is the version with Winchester support that boots to floppy. The boot sector it creates is interesting... I created a floppy disk image based on this and tried to boot it in xbeaver with my standard config, whilst the Simon ROM attempted to boot it, it failed with a corrupted error message.
Code:
6d 47 31 00 01 b7 20 01 3c 08 3e 0f d3 bc cd 1f 00 b7 28 07 3e 03 d3 bc c3 00 f0 08 c3 00 eb 21 00 d5 01 e4 01 1e 13 db e5 07 16 82 30 02 16 88 08 d3 e4 08 78 d3 e2 7a d3 e0 18 02 77 23 ed 78 28 fc db e3 fa 3c 00 db e0 e6 fc c0 04 78 d6 0a 20 22 47 3a 7e 00 b7 28 0e cb 5a 20 04 08 f6 08 08 7a f6 0c 57 18 0d 3e 5b d3 e0 3d 20 fd db e0 cb 47 20 fa 1d 20 b9 af c9 00 00 00 ...