Yes, with some relatively minor caveats, mostly having to release memory yourself.

Also, the arc/orc GC is shaping up and already allows you to use exclusively reference counted memory management - so, efficient and perfectly deterministic timing but still get automatic memory management. (As usual, if you introduce cycles, it becomes more complicated)

And the Nim compiler elides many ref/unref ops, as well as keeping objects thread-local, so most performance objections to ref counting don’t actually apply. (.... and you have a choice of other automatic GC modes, including “none”)