Today i promoted the Rainbow-100-B driver to working. I also added a fourth (PC double density) drive for better data exchange. Note that you will need IMPDRV3.SYS in CONFIG.SYS (and D: becomes unavailable).
The screenshot shows a Rainbow-100 B with amber monitor, mounted hard disk and real time clock. DC.COM (a fast, free Norton Commander clone) is running under CodeBlue (a 3rd party PC emulator). Most non-graphical applications work.
There is a FreeDOS image mounted on F: (you cannot boot that, before anyone asks)... Noticed that DIPs are a bit garbled in newer builds. They used to be aligned according to the order of the DIP macros.
P.S.: the serial port still needs some love.