Depends on when the people did this and how complex the mechanism were at the time. I do remember just learning about JMP in assembler and that you could bypass a lot of stuff by changing a true to false or vice versa. Not exactly rocket science. (Not saying this to downplay anything, but what seems magical to many non-techies was actually very easy to do if you knew the trick, and it already worked for like 30% of the games - I'm not talking about the real stuff later on, not even sure how complicated NoCD was.)
On the other hand, probably 15-20 years after I had last used a crack for a game I had to implement some basic protection like this into a piece of software (more like: make sure the customer will not run this demo version forever) and it was fun to discuss in the team what we all remembered from back then and which measures were adequate to implement.
On the other hand, probably 15-20 years after I had last used a crack for a game I had to implement some basic protection like this into a piece of software (more like: make sure the customer will not run this demo version forever) and it was fun to discuss in the team what we all remembered from back then and which measures were adequate to implement.