There are various types of random access memory. The latest motherboards are equipped with DDR2 or DDR memory. Some are even equipped with RAMBus memory. The oldest ones actually have SDRAM connectors, or even EDO RAM connectors.
DDR, SDRAM or RAMBus memory modules can be inserted in memory slots one at a time. It is not recommended to insert memory modules of different types (and brands), for the following reasons:
To insert DDR, RAMBus or SDRAM,memory modules just pull open the clips located at each end of the slot, place the memory module straight down into the slot, making sure it is in the correct position (one or more notches between the pins prevent the module from being inserted the wrong way around).
DRAM or EDO RAM must be inserted in pairs, i.e. for 32MB you should install 2 16MB modules.
Inserting EDO memory is quite tricky. Place it into the slot at a 45Â° angle, then click it in place horizonatally.