Reading flipped 5.25" disks using two Teac 5.25" drives
When trying to use a standard PC floppy drive to read flipped disks (e.g. for reading the B-side of an old C64/1541 or Apple ][ disk), it will usually fail due to the missing index signal. This was no problem for the Commodore 1541 or disk ][ drives, which did not even have a sensor for the index hole. Unfortunately, PC floppy drives require this signal in order to work properly.
Technically, the index hole is detected by a light barrier. A signal is required for the floppy drive to work, but this signal does not have to be in sync with the actual rotation of the floppy disk when reading 1541 or Apple ][ disks. If you still own two old 5.25" Teac drives, one drive might be used to provide the signal not only for itself, but also for the other floppy drive. To do so, a single-wire connection must be made between the two floppy drives. The following changes have to be done:
No guarantee can be given that this solution works for you. I have tested it using two Teac FD-55GFR drives (143U and 193U), and it seemed to work properly.
Another solution can be found here. Although it was developped for the Catweasel floppy disk controller, it should also work with Disk2FDI.
email: markus.doetsch*gmx.net (please replace * by @)