The new motherboards in computers now support the operation of two memory modules running together in a dual-channel mode. To accomplish dual-channel functionality, the RAM must be identically matched. So you would need to buy two matched modules of 512MB or two matched modules of 1GB. To insure the RAM you receive is matched it is often better to buy the kits, often the item description will say they are good for  dual-channel use. If not and you are concerned, ask the seller.

Increased bandwidth and improved performance is a big benefit of dual-channel mode. To find out if your system supports dual-channel mode, we suggest you refer to your computer's manual. The newer the computer, the more likely it is to support Dual-Channel use.

Dual Channel Upgrade Kits