I don't think that tri-state logic is used in ICs anymore (?).
EDIT: http://vswww.kaist.ac.kr/ENGLISH/old_lecture/ee878-2002/lect...
It probably does not imply that the chip is indestructible through microcode though.
EDIT: http://vswww.kaist.ac.kr/ENGLISH/old_lecture/ee878-2002/lect...
It probably does not imply that the chip is indestructible through microcode though.
Selecting a register through a tri-state based bus demands a circuit with a O(1) critical path. Selecting a register through a logical selector demands a circuit with O(log n) critical path, and a large constant factor.