Depends what you mean, it isn't necessarily related to the frequency.

http://www.tomshardware.com/answers/id-2201606/cas-latency-speed-ram.html

the access latency of the RAM depends on both the timings and the frequency, not just the timings. according to him every CL10 kit will have the same access latency... so a(theoretical) 10-10-10-29 kit at 4000MHz will have the same latency as a 2100MHz kit with the same timings, which it wont, because timings are in clock cycles and not NS