3 ms·

Does anyone know how this relates to what the Burroughs B5500 and B6500 operated?

• gumby 9y ago
  This is very similar to the Burroughs approach that later influenced Multics and the lispm architectures (and is available in some RISC-V versions). Notably Intel used this in the unfortunate iapx 432 and cleverly built some of this approach in their segmented memory model). However by the late 1970s it had been figured out that you could do some of these tricks without dedicated hardware support (mask-boxing of integers, for example on processors that ignored unaligned access you could use the least significant bits for tagging; on ones with address spaces less than the word length you could often do the same with the upper bits). These bits could be used by GC and/or for fast type systems, and by the mid 1980s had pretty much wiped out the advantage of dedicated hardware for Lisp implementations (the lispms started out much faster at tag manipulation but the weight of work on the general purpose machines caused the latter to get better (and cheaper) much faster). The bigger advantage of hardware support IMHO is the security opportunity for capability management.