> "A certain amount of knowledge you can indeed with average faculties acquire so as to retain; nor need you regret the hours you spend on much that is forgotten, for the shadow of lost knowledge at least protects you from many illusions."

--William Johnson Cory

All programmers do not need to know the many details Drepper goes into about cache refreshes and dirty bits, it is true. But most programmers will care about performance at some point, and most of those will be helped by even vague memories about the memory hierarchy and remembrances of how large the performance penalties of cache misses are. Even inklings can be enough to motivate someone to reorganize their loops, or to investigate cache-oblivious algorithms (which are a high-level topic on their own).