Есть такая штука, как мануал.
прочтите 11ю страницу. там указаны строгие ограничения накладываемые на память:
Due to CPU limitations, read the following guidelines before installing the memory in Dual Channel mode.
Dual Channel mode cannot be enabled if only one DDR3 memory module is installed.
When enabling Dual Channel mode with two memory modules, it is recommended that memory of
the same capacity, brand, speed, and chips be used for optimum performance.
• If one or two single-sided memory modules are to be installed, be sure to install it/them in the DDR3_1
socket or/and the DDR3_3 socket. If three single-sided memory modules are to be installed, two of them
must be installed in the DDR3_1 and DDR3_3 sockets. Due to a hardware limitation, if you have already
installed two double-sided memory modules, any additional memory module will not be supported.
• If four DDR3 1333 MHz memory modules are installed, the maximum memory speed will be limited to
1066 MHz