Apple Mac 5260/100 - Manual (Page 11)

Basics Processor Direct Slot (PDS) - 9
Processor Direct Slot (PDS)
The LC-PDS is compatible with the PDS in the Macintosh LC
family of computers, but it is not a true PDS. Like the
expansion slot in the other models in the Power Macintosh
and Performa 5000 series, this expansion slot supports
many PDS cards designed to operate with the MC68030 bus.
While the I/O expansion slot accepts PDS cards designed for
the Macintosh LC family of computers, some of those cards
do not work. PDS cards designed to interact with the main
processor—to provide, for example, a RAM cache or an
FPU—will not work in the I/O expansion slot.