LC PDS Ethernet card. PDS connector is at bottom left of photo. The card was mounted parallel to the main logicboard, unlike most computer busses where cards are inserted at right angles to the motherboard.

Processor Direct Slot or PDS, was a solution (actually, a whole number of different solutions) introduced by Apple Computer, in several of their Macintosh models, to providing a limited measure of hardware expandibility, without going to the expense (in both desktop space and selling price) of providing full-fledged bus expansion slots. Image File history File links Download high resolution version (1446x865, 183 KB) Summary Apple Macintosh LC PDS (Processor Direct Slot) ethernet card. ... Image File history File links Download high resolution version (1446x865, 183 KB) Summary Apple Macintosh LC PDS (Processor Direct Slot) ethernet card. ... Apple Computer, Inc. ... The first Macintosh computer, introduced in 1984, upgraded to a 512K Fat Mac. The Macintosh or Mac, is a line of personal computers designed, developed, manufactured, and marketed by Apple Computer. ... In computer architecture, a bus is a subsystem that transfers data or power between computer components inside a computer or between computers. ...

Typically, machines with bus expansion slots would have more than one of them. However, there was never more than one PDS slot. 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 mostly just gave direct access to signal pins on the CPU.

Thus, PDS slots tended to be CPU-specific, and a card designed for the PDS slot in the Motorola 68030-based Macintosh SE/30 would not work in the Motorola 68040-based Quadra 700. Motorola 68030 Processor from a Macintosh IIsi The Motorola 68030 is a 32-bit microprocessor in Motorolas 68000 family. ... The Motorola 68040 is a microprocessor from Motorola. ...

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, and later even a 68040, and later even a PowerPC processor ways were found to keep the PDS slot compatible with the original LC, so that the same expansion cards would continue to work. Motorola 68020 The Motorola 68020 is a microprocessor from Motorola. ... Macintosh LC sans display, keyboard or mouse The Macintosh LC (meaning low-cost color) was Apple Computers product family of low-end consumer Macintosh personal computers in the early 1990s. ... IBM PowerPC 601 Microprocessor PowerPC is a RISC microprocessor architecture created by the 1991 Apple-IBM-Motorola alliance, known as AIM. Originally intended for personal computers, PowerPC CPUs have since become popular embedded and high-performance processors as well. ...

The current standard for adding video cards to PCs, known as Accelerated Graphics Port or AGP, may be considered to be somewhere in-between a PDS and a bus. Like a PDS, there is no bus arbitration, so you can only have one AGP card per system; however, it works at a higher level than a PDS, in that it is CPU-agnostic, and AGP cards can be designed to work across Intel- or AMD-based PCs as well as Apple Macs and other computer platforms. AGP slot (maroon), although the color is usually brown. ...