This 4GB RAM is 100% compatible with the MSI CSM-B85M-P32. For assistance in selecting the right RAM, we offer you faster 1600MHz memory for your system. Thanks to the backward compatibility of our RAM with 1333MHz, you can also mix it with existing 1333MHz memory. ECC memory provides higher security through error detection and correction. The ECC function is supported when all existing memory is equipped with ECC. You should use UDIMM ECC RAM if your existing memory is ECC-equipped. It is possible to use different RAM sizes in the slots. The Dual Channel Mode is also supported by Intel Flex Memory Technology. When using different memory capacities, ensure that the memory in memory channel A is larger than the memory in memory channel B.