Zak Kemble wrote a post on his blog showing how he modified the RAMs Serial Presence Detect (SPD) data:
Recently I brought some low-power Mini-ITX motherboards; a Gigabyte GA-N3050N-D3H and a Biostar N3050NH. These boards take SO-DIMM DDR3 RAM, the sort found in laptops. The boards are both pretty much the same, however the Gigabyte board lacks quite a few BIOS features and settings that the Biostar board has. One of those missing features was being able to set the RAM frequency. I wanted to run the RAM at its lowest frequency of 800MHz, but the Gigabyte board would run it at the its normal frequency of 1600MHz. Running at 800MHz reduced idle power consumption by about 0.12W on the Biostar board, a ~2% reduction… yeah ok, it’s a teeny tiny amount, but it was just a matter of flicking a switch.
To remedy this it looked like I was going to have to modify the RAMs Serial Presence Detect (SPD) data.
More details at Zak’s blog.