However, it has an unusual architecture in which all programs run in a bytecode-based virtual machine, comparable to Java or dotnet. The 128 bit pointers are only used in the virtual machine. The underlying physical hardware had 48 bit addressing initially (starting in the late 1970s); in the 90s they switched physical hardware to support 64 bit addressing

Also, even though the pointers are 128 bit, many of the bits in the pointer are reserved for future use. Partly it was an exercise in extreme future-proofing. Partly because they use tag bits to mark valid pointers in memory (to stop programs from forging pointers), but they only have one tag bit reserved for every 16 bytes of RAM, so pointers must have 16 byte alignment.