Mobo: ASUS P5W DH Deluxe in Dual Channel Memory Mode: Is there no BIOS setting you have to update in order to run it in Dual Channel Memory Mode? Just upgraded to 2 kits of 4 GB each.
No, there is nothing to change in the BIOS in order for the RAM to run in dual channel mode. That's all determined by using the correct RAM slots as described in your motherboard owners manual.
shortstuff_mt is right. The BIOS takes care of the change - it automatically will switch to dual-channel mode IF you mount the right modules in the right slots. And that will show up in displays of memory operating mode.