Dunno, a 128bit integer add is essentially 2x as expensive as a 64 bit one, a multiply is 4x. We've already had SSE in the early 2000s that could do computations like this in a single cycle (tho on multiple 32 bit numbers, not 128-bit ones).

I think on x86, we're still limited to 48 bits of address space on 64 bit systems, not sure if this has changed, but even 64 bits is so vast (16exabytes) , that you'd need a supercomputer with a single address space to fill it, but at least the latter is practically realizable.

X86 CPUs with support for 57 bit of virtual address space have been produced by both Intel and AMD: https://en.wikipedia.org/wiki/Intel_5-level_paging.