Drive Swapping Daughter Card for Apple’s DISK ][ INTERFACE

KiCAD Ray-traced Rendering

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.

X-CHANGE ][ Installed on a DISK ][ INTERFACE card

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

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