I would not assume they just use bits in the address word for the tag. LPDDR6 includes 16 bits of host-defined metadata per 256 bits of data. Systems can use t

I would not assume they just use bits in the address word for the tag. LPDDR6 includes 16 bits of host-defined metadata per 256 bits of data. Systems can use that for ECC, and/or for other purposes, including things like tagging memory. DDR6 will likely include a similar mechanism. SECDED ECC requires 10 bits, leaving you 6 bits. That's enough for one bit per aligned address word, which is probably used to denote "valid pointer" like CHERI.