The SPARC CPU was designed to make use of this. Alignment checking was enabled by default, the tagged add/sub instructions required that the tag in the lower tw

The SPARC CPU was designed to make use of this. Alignment checking was enabled by default, the tagged add/sub instructions required that the tag in the lower two bits for an integer was 0, tags for pointers were expected to be 3. Lisp Machines were word addressed so the technique wouldn't work for them.