> Of course, some kinds of system designs burn physical memory addresses faster than you'd expect. In particular, suppose you build a system with multiple mem

> Of course, some kinds of system designs burn physical memory addresses faster than you'd expect. In particular, suppose you build a system with multiple memory systems. A minimal/natural approach is to use the high-order bits of an address to select the memory to be accessed. We're already starting to see this regarding some of the up-and-coming technologies like CXL and Gen-Z (which have now been merged). The idea is for a fabric consisting of multiple machines to share a common address space, and with the transition from 48-bit virtual addresses to 56-bit virtual addresses happening soon-ish, there's not many bits in the address space left to leave a machine identifier in your 56-bit address.