It depends on the strength of the components of the chip..
Each is generally (but not always) weaker/stronger than another.
The K chips allow different speeds for the core vs the uncore (cache and imc).
When overclocking non-k chips the core and uncore are (so far) locked 1 to 1.
You can slow down the imc by running memory below 2133 but that is certainly an undesired end result/workaround.
edit - usually the importance to performance from high to low - core, then cache then imc/memory but it depends on the load - if a lot of disk access is required - even your HDD (hopefully SSD) can be the bottleneck.
Edited by SteveRo - 2/5/16 at 4:52am