Total Annihilation was asynchronous, Supreme Commander was synchronous lockstep ...

Total Annihilation was asynchronous, Supreme Commander was synchronous lockstep (sending user interactions only), Planetary Annihilation said they were client-server, with the server only sending updates for units a player could see.

Still a Total Annihilation fanboy at heart.

https://www.pcgamer.com/planetary-annihilation-interview/2/

https://www.forrestthewoods.com/blog/tech_of_planetary_annih...