Q: How can I attach a 3.5 inch disk drive to my Rainbow?
The Rainbow can actually handle double density 3.5 inch disk drives. To make this possible, you need one of two things: the Suitable Solutions upgrade kit for the Rainbow or IMPDRIVE by M. Warner Losh. The first is a lot harder to find, so you should probably rely on the latter.
IMPDRIVE is available on the major Rainbow archive sites. It is considered shareware and the author requests a small registration fee. The program allows the attachment of a 3.5" double density, a 5.25" double density, and a TEAC 55F 5.25" drives. The program is a simple driver that is placed in the the config.sys. The program works only under MS-DOS 3.10b.
To connect the drive, you need a standard straight-through 34 pin cable. Just plug one end into the Rainbow floppy controller port (usually the C-D connector) and you're finished. To connect older 5.25" drives, you need a 34 pin to 34 card-edge straight-through cable. You can connect 2 drives at once, but you need to remember that the cable, which has two connectors, must be straight-through.