just do the same run with eg 2 x 1 Gb and 2 x 2Gb , you will get far better scores clock for clock in PI32 with the 2GB dimms.... same for eg for S478, do pi32mb with 2 x 256 or with 2 x 512Mb, world of difference. Even Memtest gives far better bandwith with 2gb dimms over 1gb ones...