I recently acquired a DEC Rainbow 100 Model B, with a working RD51 disk. The disk is running MS-DOS 2.11. I want to preserve the contents of the disk before it fails. A while back I acquired the MFM Emulator board designed by David Gesswein and built it. Mine is an older revision of the board and it works really well. I have also bought the later board but I have yet to build it.

I connected it up as you can see in the picture below. In this case I connected the floppy power connector to the emulator board, and of course the RD51 to the MFM connectors.

You can see that the BeagleBone Black that runs the software is connected to a network cable. I use PuTTY to log into the BeagleBone Black over SSH and run the commands needed. To image the disk I used the following commands:

./setup_mfm_read
./mfm_read -d 3 --ana --emu /sd/<file>.dsk --ext /sd/<file>.ext --note "<description>" | tee /sd/.log


After that I shut the machine down, and discharge the reservoir capacitors with a resistor, just to speed things up. The later revision has a jumper for this I believe.

Now is the time to run the Rainbow from the emulated disk. To do that you just connect the MFM connectors to the edge connectors on the emulator board, connect the power and power up.

This however does not automatically start a disk emulation however. I have not set that up because I want to use it to emulate different disks at different times. So I still need the network cable to be able to login and run the emulation this time. The commands to emulate the disk for the Rainbow are:

./setup_emu
./mfm_emu -d 1 -f /sd/<file>.dsk


Note that I have to use drive id 1 for this to work on the Rainbow. Here it is working:

The Rainbow thinks it has a hard disk, but really it is just an emulator!