Not even PCMark 05’s memory benchmark seems to be impressed by the missing dual channel mode.
We found the same results in the overall score.
Sandra 2008 does shows a distinction between single channel and dual channel DDR2-800 operation: 5.7 GB/s versus 6.4 GB/s is a clear difference, but far from the theoretical 50% gap.
The two application benchmarks 3DSmax and WinRAR don’t suffer much if dual channel memory mode is disabled. In particular, we did not expect WinRAR to remain at roughly the same performance when run in single channel memory mode.