The Apple //c cannot boot from external floppy. (exception is the original ROM255 release).
PR#7 will crash the system. Here is a small program that detects the type of Apple // being used, and if running an Apple //c, will detect the ROM version, and then execute a small machine language code to boot a PRODOS image from the external drive.

In this demonstration, a DOS 3.3 disk is in the internal floppy drive. A wdrive is connected as the external disk, with ADTPro mounted as the floppy.

The non apple released ROM4x does support booting from external floppy, but requires opening up the case, and replacing a chip. This program can be left in the internal floppy disk, and be automatically run, so that second floppy can boot using a software solution. It does not support non-PRODOS volumes.

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