Apple Performa 6400/180 - Manual (Page 228)

Additional Procedures 6500—Software Installation Errors and L2 Cache Identification
If this number, not counting
the Q or any other letters
present, has four digits, the
cache is incompatible with
an OPC logic board. Replace
this L2 cache DIMM with
part number 661-1477.
IDT 74FST
3384Q (Use this number to identify a problem DIMM.)
F9637BFU
IDT 74FST
3384Q (Use this number to identify a problem DIMM.)
F9637BFU
IDT 74FST
3384Q (Use this number to identify a problem DIMM.)
F9637BFU