Editing Processor Direct Slot (section)

== Overview ==
Typically, if a machine had bus expansion slots it would feature multiple bus expansions slots. However, there was never more than one PDS slot, as rather than providing a sophisticated communication protocol with ''arbitration'' between different bits of hardware that might be trying to use the communication channel at the same time, the PDS slot, for the most part, just gave direct access to signal pins on the CPU, making it closer in nature to a [[local bus]].

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 [[Macintosh Quadra 700|Quadra 700]].

The one notable exception to this was the PDS design for the original [[Motorola 68020]]-based [[Macintosh LC]]. This was Apple's first attempt at a "low-cost" Mac, and it was such a success that, when subsequent models replaced the CPU with a 68030, a 68040, and later a [[PowerPC]] processor, Apple found methods to keep the PDS slot compatible with the original LC, so that the same expansion cards would continue to work.