He may have meant this when he created the slide, but precise numbers here seem less important than relative magnitude as long as one is reasonably close.<p>One could be a few ns off on how long a L2 cache lookup takes, and endure in all but the most time-critical situations. Far bigger problems occur when one failed to account for drive seeks being around eight orders of magnitude slower than L2 cache lookups.<p>It doesn't strike me as a list of numbers to memorize and be able to recite, but more the sake of cultivating an intuition of where to start looking for places to optimize communication, and the relative order of things one should focus on.