The Sun Microsystems Rock processor had I guess, validation? Rather than re-order instructions, you just speculatively execute instructions, issue you memory op

The Sun Microsystems Rock processor had I guess, validation? Rather than re-order instructions, you just speculatively execute instructions, issue you memory ops but don't stop and wait, called "hardware scouting". If after everything resolves, you find your prediction was wrong, you rollback. So it's a kind of Transactional Memory approach, and if validation fails, you re-execute the same sequence of instructions, but the branches are different. https://en.wikipedia.org/wiki/Hardware_scout https://en.wikipedia.org/wiki/Hardware_scout