sdram controller

Alright, after having perused various datasheets, I have a (perhaps) obvious question with regards to clocking and latency. Let me see if I can phrase this correctly:

Given a certain clock frequency, you can calculate how many clocks you'd need in order to satisfy timing requirements. For example, a tRCD of 15ns at 100mhz would imply 2 clocks, which would give you 20ns and therefore meet the timing requirements, whereas a 200mhz clock would imply at least 3 clocks. These figures are all listed in the datasheets as well as the timing in nanoseconds.

My question is whether or not SDRAM needs to be clocked or if you just need to satisfy those timing requirements. In the example above, you could either wait two clock periods or, if you would lower the clock speed (I know, different discussion) to say, 25mhz, you could submit two commands back-to-back as there would be ample time to satisfy the timing requirements.

So I guess to sum it up, are commands and data (in/out) the only ones that need to be clocked or do you NEED to clock in NOPs as SDRAM is a synchronous, pipelined architecture?

-Mux