Server Board S2600WT2R unable to set clock speed to 2400.

I have an Intel® Server Board S2600WT2R

I have set the Memory Operating Speed in the bios to 2400, but dmidecode reports that "Configured Clock Speed: 2134 MHz".  If I set the clock speed in the bios below 2133, the clock speed changes appropriately.  I have been through the BIOS manual and I believe I've set everything up properly.

I know what my RAM (Kingston KVR24R17D4/16) is not on the Approved Memory List.

Thank you for your time.