Right, so it looks as if the BIOS we had (1.21) was from a PC1 HD, there are now two more revisions from "plain" PC1's.
Simone says "In effect, the PC1 BIOS is different, [...]Not much difference but they lack HD support, obviously."
The new added BIOS versions (1.06 and 1.07) contain the string "Fixed Disk", though.
Next, Simone wrote "The 8042 keyboard controller is protected and it was programmed to take into account of Joystick movments (translated to keycodes) and mouse Keys. I'll bet that the Olivetti M24 (or AT&T 6300) keyboard controller is quite the same chipset, so you can try it if you can find something.
The mouse X/Y coordinates are directly supported from the YAMAHA video chip (yes!). I wrote a specific mouse driver (in assembler) for it that take advantage of this chip and his mouse (much smaller and faster of the originar mouse driver)"
I've uploaded his driver and asked him to share his source code, so I hope this is forthcoming.
The video chip supports a graphical mouse cursor over text mode, as seen here: https://www.youtube.com/watch?v=-8K...ZY2p9HIxVd99oXEqkDePhvUSTcnoKtpKNmpNVd4Y
Thanks to both crazyc and Simone2013!!!