Drive Swapping Daughter Card for Apple’s DISK ][ INTERFACE
This little card was designed by me to address and issue with my very odd Apple IIe computer. Namely the fact that my 2 “Floppy” drives aren’t both floppy drives.
One drive is a tried and true Disk II drive, but the other is an SDISK II which I built using the design of Koichi Nishida.
Since the original design of the DISK ][ INTERFACE only permits booting from Drive 1, this presented a problem if I wanted to boot from the “other” drive.
I initially considered simply putting a switch in place to exchange control from one port to the other, but decided that I wanted a “fail-safe” built in, so the drives could not be swapped while a drive was in use.
Enter the X-CHANGE ][. A switch closure on the pins labeled “SSW1” will reverse Drive 1 and Drive 2 assignments ONLY if both drives are OFF and have been off for 5 seconds.
The delay prevents switching in the middle of large file operations.
The remaining two pins are an open collector output and +5v to allow for an LED to show when the drives are actually reversed.
As pictured below, the board plugs into the socket of the DISK ][ INTERFACE’s 74LS132 (A2) with that chip being relocated onto the daughterboard.
Technically, this should work on clone cards, and even Uni/Duo Disk cards (the kind with a DSUB 19 connector) but only if there is a socket for the LS132 chip.
Assembled Board (NO SWITCH PROVIDED) – $24.00