MostOfMyMac.com

The iMac (Early 2006) computer has two SDRAM slots in the bottom of the computer. The iMac ships from the factory with at least 512 MB of DDR2 SDRAM installed into the top slot. (The computer may come with more RAM in the top slot or RAM in the bottom slot, depending on how you ordered the computer from Apple.) The iMac (Mid 2006) ships from the factory with at least 512 MB of DDR2 SDRAM, in two 256 MB DIMMs; one in each of the memory slots. Note: If you upgrade the memory in your iMac (Mid 2006), make sure you have matching size SO-DIMMs in each slot for best graphics performance. The iMac (17-inch Late 2006 CD) ships from the factory with at least 512 MB of DDR2 SDRAM, in two 256 MB DIMMs; one in each of the memory slots.