the new opteron have 4 mem channels per CPU. general guidelines for Intel Nehalem:
one DIMM in each mem channel results in 1333 Mhz more than 1 DIMM in each channel = 1066Mhz more than 2 per channel = 800 Mhz (max is 3 per channel for Nehalem Xeon 55XX)
thus the bandwidth is reduced by population
is there a similar recommendation or guide for AMD Opteron 6100 series?