The clamshell iBook's logic board, which is based on the Unified Motherboard Architecture (UMA), still has untapped reserves: For cost reasons, initially only 32MB RAM (later 64MB RAM) was installed as main memory via a bank of 4 SAMSUNG chips (two above, two below) on the logic board soldered. Up to 512MB could be retrofitted via a free slot for a 144-pin SODIMM module.
What many people do not know: On the underside of the logic board, 4 free slots for RAM chips can be clearly seen in the circuit board layout - a resource that was kept free for another edition that was never realized.