Better than POSIX?

In the 80's a Lisp machine would start in the few seconds it took the monitor to warm up because it was almost always started from what we would now call suspend-to-disk. Loading a new image could take half an hour or more but you only did this a few times per year.

Garbage collections caused zero delay, as incremental garbage collection was supported in microcode.

Just like today, if you needed a coffee break in the 80's you had to find something huge to compile.