All iBook models come with memory already installed on the logic board. This memory can't be removed. However, all iBook models also have a single SO-DIMM slot for memory expansion (G3-based iBook models use PC100 modules; G4-based iBook models use PC2100 modules). If there is a memory module installed in this slot, you must remove it before you insert a replacement module.
The memory slot in the iBook G4 (12-inch late 2004) can accept an SDRAM module that meets the following specifications:
Double data rate (DDR) small outline dual inline memory module (SO-DIMM) format
1.25 inch or smaller
128, 256, 512 MB, or 1 gigabyte (GB)
PC2100 DDR 266 Type RAM
The maximum amount of memory you can install is 1.256 GB, using one 1 GB DIMM ...