This message was posted on behalf of Intel Corporation
Let me share with you the board Technical Product Specification document that you can download from the following URL: http://www.intel.com/content/dam/support/us/en/documents/server-products/server-boards/S2600WT_TPS_R1_4.pdf
From page 22 you will find the Memory Subsystem information and the population rules. Just as a hint the memory max transfer clock speed depends on the processor version so 2400 MT/s is only supported on Xeon E5-2600v4 family processors.
Hope this helps.
Thanks Jose, my server is using a Intel(R) Xeon(R) CPU E5-2690 v3 CPU, which is limiting my RAM clock speed.