I love the responses in this thread. Turned out that my "Fermi estimate" was wrong, by about a factor of 100x. A simple back-of-the-napkin maths is that for a

I love the responses in this thread. Turned out that my "Fermi estimate" was wrong, by about a factor of 100x. A simple back-of-the-napkin maths is that for a system with 30GB/s memory bandwidth and 32-byte cache lines works out to about a billion I/O operations per second. This would be a typical laptop system, or the like. However, 100ns per read is still a valid scenario for a single-threaded program "chasing pointers" as in a linked-list. I think it's still fair to say that an un-optimised single-threaded program accessing memory randomly is only 10x faster than a parallel program efficiently utilising a modern NVMe SSD. The corollary is that there is (still) no scenario where an SSD would "beat" the performance of RAM since the worst-case for RAM still beats the best-case for SSD.