What about multithreading? An OS can read from an SSD then context switch to do useful other stuff until the data comes back. Once the OS issues a request to (relatively) slow memory, the only thing that can use that core are other instructions in the pipeline and other hyperthreads; i.e no other OS threads allowed.
The fastest NVMe SSDs are already right around the threshold where there isn't time to complete a pair of context switches before you get the data back, and the difference in latency between polling or waiting for an interrupt is significant. These Optane DIMMs should be fast enough that only hardware-managed context switches like hyperthreading/SMT are usable without performance loss.
