Memory Type: SDRAM, PC133, SDRAM (non-ECC)
Maximum Memory: 512MB
To access the second slot requires the removal of the microprocessor board which should only be performed by authorized Apple service technicians.If you are using OS 8.6 or greater, ensure you have firmware 1.2 or greater installed.
Memory or DRAM is the "working" memory of the computer. It's used to store data for programs (sequences of instructions) on a temporary basis.
video - installing memory