
Memory Type: DDR2 PC2-6400, DDR2 (non-ECC)
Maximum Memory: 4GB
Slots: 2
Each memory slot can hold DDR2 PC2-6400 with a maximum of 2GB per slot.*
*Not to exceed manufacturer supported memory.

Please check the memory frequency of your iMac. Your memory upgrade needs to match the frequency of the installed memory. Note that the memory speed and the bus speed can be different.

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