Apple Performa 6400/180 - Manual (Page 42)

Basics Dual In-Line Memory Modules (DIMMs) - 40
Power Macintosh 6500
The 8-byte DIMMs can be installed one or more at a time.
The logic board supports only linear memory organization,
and no performance gains result when two DIMMs of the
same size are installed. Any supported size DIMM can be
installed in either DIMM slot, and the combined memory of
all installed DIMMs is configured as a contiguous array of
memory.
The DIMM slots accommodate 168-pin, 5-volt, fast-paged
and EDO DRAM DIMMs. The largest DIMM supported is a
two-bank DIMM holding 64 MB.
Note:
The logic board does
not
support 3.3-volt EDO DIMMs.
These DIMMs don’t mechanically fit into the DIMM slots.