The PowerBook G3 Wall Street can be upgraded to 512MB by using two 256MB modules (512MB Kit).

Standard Memory
32MB or 64MB Removable
Maximum Memory
512MB
Memory Expansion (No. of sockets)
2 Expansion Sockets
Memory Expansion
Install 1 at a time
Memory Sizes
64MB | 128MB | 256MB | 512MB Kit
Memory Speed (Type)
PC66