Building new system. Have Athalon 64 bit dual core Processor (2.6 Ghz). 4 slots for memory. Have matched pair of OCZ 4GB (2X2) on order; one 1GB stick operating in single core mode now. Also have some other 1GB sticks in inventory. If I were to use the 1 GB sticks or any other combo am I right in thinking that the first 2 banks have to be matching, and when I get the OCZ-will the proc recognize the pair of 2GB and use dual core mode. Or is there a setting in the bios I need to change? Thanks for the help... seems confusing to me.

This might help you--> MEMORY FAQ (please read before posting)

Also, referring to dual-channel systems

"Dual-channel DDR RAM has a misleading name and refers to the fact that dual-channel motherboards have two memory channels instead of one, making them more efficient than single-channel motherboards. So it's not really the RAM that's dual-channel, it's the motherboard, and as such, the RAM you use on a dual-channel motherboard doesn't need to be the same brand, have the same timings, or even the same speed. Many retailers sell dual-channel RAM in expensive pairs and imply that these pairs are the only way to ensure the fastest possible performance, but the reality is that a motherboard's dual-channel capabilities are what make for speedier operation."

Computer Power User Article - Wrong-Way RAM