The Amiga was the first consumer OS with pre-emptive multi-tasking, absolutely, but BeOS was the first with such aggressive multi-threading and exceptional supp

The Amiga was the first consumer OS with pre-emptive multi-tasking, absolutely, but BeOS was the first with such aggressive multi-threading and exceptional support for multiple CPUs. On BeOS the menu UI had its own thread. Even if the app was busy thinking it still wouldn't jam. That wasn't the case on other operating systems that simply had multi-process support.