The G4 iBook has one memory socket and can be upgraded using a 256MB,512MB or 1GB DDR module

Standard Memory
512MB soldered on board
Maximum Memory
1.5 GB
Memory Expansion (No. of sockets)
1 Expansion Socket
Memory Expansion
Install 1 at a time
Memory Sizes
256MB | 512MB | 1GB
Memory Speed (Type)

All 14" models except the 1.42GHZ model use PC2100 ram. The 1.42ghz model uses PC2700 RAM.

All 12" models except the 1.33GHZ Models use PC2100 RAM. The 1.33GHZ model uses PC 2700Ram.