The Processor Direct Slot or PDS, introduced by Apple Computer, in several of their Macintosh models, provided a limited measure of hardware expandability, without going to the expense (in terms of desk space as well as selling price) of providing full-fledged bus expansion slots. Thus, PDS slots tended to be CPU-specific, and therefore a card designed for the PDS slot in the Motorola 68030-based Macintosh SE/30, for example, would not work in the Motorola 68040-based Quadra 700.