[kibwen]

> Maybe we will see the widespread use of 128-bit computers during our lifetimes.

Not at current rates of demand. During the 80s and 90s demand for RAM increased a thousandfold per decade, from 1 KB to 1 MB to 1 GB by 2000-ish. At that rate we'd expect normal users to exceed a 64-bit address space by the 2040s. But instead demand has slowed dramatically, and after 20 years a power user might only have 64 gigs, or 128 if they're feeling spicy. Apple is still selling computers with only 8 gigs of un-upgradeable RAM. And as for virtual memory, I doubt that consumer machines have any legitimate reason to chafe against the 16-exabyte limit (until such time as we're selling zettabyte hard drives, which is fantasy at this point). Servers and supercomputers might be a different story, but even servers are going to be loath to pay the cost of halving the speed of ordinary operations just to double the addressable memory space.

[Dagonfly]

"Widespread" was maybe the wrong word, I was mostly imagining virtual memory on servers.

Currently, not all 64 bits are available for user-space VAs. Even with Intel's 5-level paging you can "only" get 56-bit (128 PB) of virtual addresses. On ARM they reserved parts the top-level byte for memory-tagging as well.

Remember with pointer tagging and overcommit you might have orders of magnitudes more VA address space used than available RAM. Exhausting 128 PB of virtual addresses in the next 40 years does not seem unfeasible to me. CHERI already exists in some niche.