Well 1155 systems don't increase bandwidth when overclocking due to limited base clock so one has to raise the ram clocks separately compared to 1366 and 1156. Most don't ever see 25.6gb/s until they use high end low latency ram. 18gb/s is common.
18gb/s is common
I did not understand
Check the benchmarks on THG, X-Bit, and AnandTech. They all got charts and reviews about 1155 SB and IB memory scaling.