OC the ram does not turn off turbo or idling features. Ram speed is independent from the cpu on sandy bridge.
I would suspect that ram to just underclock to the same as this. http://www.newegg.com/Product/Product.aspx?Item=N82E16820231416
Most of the time slower ram can overclock to higher speeds of the same model because it is usual for companies to make the same ram and price it at different speeds.