I was recently told that i5 ivy bridge's do not utilize any ram speeds above 1333, is this an accurate statement? I have my 1866 ram oc'd to 2100, and I'm being told it's not even being used. I have tried to research this with no luck. I monitor my pc during heavy tasks and see that it is using up the majority of my ram, but this info is not good enough as proof. Please help me understand whether this is true or not.
Officially, Intel support upto 1600MHz of memory and anything above that is considered Overclockin which may void the warranty. IMO, it should run upto 2133MHz or 2400MHz without any issues. Try running a CPU-Z and check the speed the memory is running at (Memory tab or the SPD tab). Usually, CPU-Z reports the real clock speed which is half the effective speed. i.e 800MHz is the real clock speed of DDR3-1600MHz.
The difference between these speeds are not noticed best by the user but the computer. So I thnk it should be working at the speed which you have overclocked it to.
Hope that helps.
Download CPU-Z - http://www.cpuid.com/downloads/cpu-z/1.65-setup-en.exe