What’s old is new again: IBM 360 architecture also only used 24 bits for addresses back in the 1960s, so you could stuff data in the upper byte of pointers. Eve

What’s old is new again: IBM 360 architecture also only used 24 bits for addresses back in the 1960s, so you could stuff data in the upper byte of pointers. Eventually, programs had to declare themselves to be in “Extended Mode” if they wanted to get access to 31-bit addressing instead.