Will Quad-Channel DRAM Work In Dual-Channel Motherboards?
When you see a four-DIMM set of DRAM advertised as quad-channel, that's marketing at work. You can easily take that same set and run one DIMM in single-channel mode, two DIMMs in dual-channel mode, three in tri-channel mode or all four in either quad- or dual-channel mode.
Each stick of DRAM is an individual 64-bit device and runs as such. On a dual-channel motherboard, with two or four modules in the proper slots, the MC (memory controller) sees all the DRAM as a single 128-bit device. If three are in an LGA 1366-based motherboard or configured as tri-channel in an LGA 2011 motherboard, then the MC sees all the DRAM as a 192-bit device. Four DIMMs set up in the proper slots of an LGA 2011 motherboard for quad-channel mode are seen as a 256-bit device, rather than four 64-bit devices.
I’ve seen many people buy a four-module set with the express purpose of using two modules in two separate motherboards. However, this is rare because, usually, the four-module sets cost a little more than if you were to buy two equivalent two-module sets. This is because it takes more testing for the manufacturers to match up modules for a four-module set.