The Apple IIGS is designed to be used with the vast majority of Apple IIe
hardware and software. However, there are some design differences that will
cause some products to be incompatible with the Apple IIGS.
When a RAM disk or ROM disk is used with ProDOS 8 and at least two disk drives
are connected to the SmartPort, the IIGS maps the second (and third) drives
into slot 2. This function will conflict with those multi-function cards
manufactured for the Apple IIe which normally reside in slot 2. Since phantom
slots are used by both the multi-function card and ProDOS 1.2, the two cannot
be used in the same machine.