How to mix DDR3 modules

In summary, there is no single DIMM per channel limit here yet: if having a good mobo with a set of top-notch DIMMs like these offerings, and willing to spend some time tuning the stuff, you can still have your 4GB DDR3 cake, and eat it with full bandwidth and low latency. But, it will be hot, take a lot of power and, last but not least, still cost hell of a lot of money