You can use a 64-bit CAS if you want to use a 32-bit epoch and a pointer compression scheme of any kind, or just a 32-bit index into regions that are thread specific. I think I did the later when I did the original work, using the core primitive to build ring buffers that have arbitrary sized slots instead of 64-bit slots (which requires a bit of additional gymnastics, but the basic trick is to have the ring index into a bigger ring that you can FAA into, where the bigger ring has more slots by at least the max number of threads (I use this primitive heavily still for in-memory debug logging). Maybe at some point I'll do an article on that too.