The PowerBook G3 Pismo can be upgraded to 1GB by using two 512MB modules.

Standard Memory
64MB or 128Mb Removable
Maximum Memory
1GB
Memory Expansion (No. of sockets)
2 Expansion Sockets
Memory Expansion
Install 1 at a time
Memory Sizes
64MB | 128MB | 256MB | 512MB
Memory Speed (Type)
PC100