Frequency is the most advertised spec of RAM. As anyone who’s dug a little deeper knows, memory performance depends on timings as well--and not just the primary ones. We found this out the hard way while doing comparative testing for an article on extremely high frequency memory which refused to stabilize. We shelved that article indefinitely, but due to reader interest (thanks, John), we decided to explore memory subtimings in greater depth. This content hopes to define memory timings and demystify the primary timings, including CAS (CL), tRAS, tRP, tRAS, and tRCD. As we define primary memory timings, we’ll also demonstrate how some memory ratios work (and how they sometimes can operate out of ratio), and how much tertiary and secondary timings (like tRFC) can impact performance. Our goal is to revisit this topic with a secondary and tertiary timings deep-dive, similar to this one. We got information and advice from several memory and motherboard manufacturers in the course of our research, and we were warned multiple times about the difficulty of tackling this subject. On the one hand, it’s easy to get lost in minutiae, and on the other it’s easy to summarize things incorrectly. As ASUS told us, “you need to take your time on this one.” This is a general introduction, to be followed by another article with more detail on secondary and tertiary timings.