Memory timings
（重定向自RAM latency）
Memory timings or RAM timings measure the performance of DRAM memory using four parameters: CL, TRCD, TRP, and TRAS in units of clock cycles; they are commonly written as four numbers separated with dashes, e.g. 7-8-8-24. The fourth (tRAS) is often omitted, and a fifth, the Command rate, sometimes added (normally 2T or 1T - also 2N, 1N). These parameters specify the latencies (time delays) that affect speed of random access memory. Lower numbers usually imply faster performance. What determines absolute system performance is actual latency time, usually measured in nanoseconds.