If you want to operate your RAM at 1866 then it is recommended that the motherboard needs to be able to support it and the processor needs to run at a speed that allows the correct combination of FSB speed and multiplier to get it to work correctly.
Otherwise check the System memory by running Memory Diagnostic Tool in Windows 8. 1 and check:
Step 1: Open the control panel and choose the System and Security-> Open the Administrator Tool which is the last option present under System and Security.
Step 2: In the administrative tools window displayed a list of options, click on open the 'Windows memory diagnostic'.
Step 3: After it, you can see the option to verify the memory errors and click the 'Restart now and check for problem' option, but before that make sure that you have saved any unsaved work running on your PC.
Step 4: Once you choose to reboot, the windows memory diagnostic tool starts verifying and restarts automatically displaying the result.