The PowerMac 7300 (1997) has 8 memory sockets arranged in 4 banks of 2. It can go to 1 Gb RAM with 8 x 128 Mb 5V 168 pin buffered DIMM modules (these are not the same as PC66 and later DIMMs).
It can interleave memory accesses between 2 modules if both DIMMs in a bank are matching -- that is they have to have the same size, speed and composition (the number of chips on the module and how the logical rows and columns are arranged on those chips.)
As far as how can you know? I don't think you can, IIRC the OS really doesn't have any reporting features to tell you if interleaving (or for that matter Dual Channel, 10 years later) is operating.