Pin 32 of the Apple II bus is a signal called /INH (short for "INHIBIT"). Some of what I found online about using this pin for an Apple II expansion card suggests it was inconsistently implemented across the various versions of the Apple II.
Pin 32: this is the INHIBIT pin on all machines. This behaves differently on all three machines: the II and II+ only allow the $D000-$FFFF ROM area to be inhibited. The IIe allows RAM to be inhibited as well, but has strange interaction with main and auxiliary memory. The IIgs only allows this signal to be used if the machine is running in slow mode.
Other references simply say that /INH disables all the motherboard memory. Which description is correct?
Also, what sort of expansion cards use /INH and how? Is it for a particular type of memory expansion card?