Nothing in OOP says that object state must be mutable. It's just as simple to have objects that always maintain their instance pointers and internal state sepa

Nothing in OOP says that object state must be mutable. It's just as simple to have objects that always maintain their instance pointers and internal state separate from one another and use message passing for transforming that state. Such an architecture is completely capable of running on multiple cores without too much context switching or other synchronization overhead issues, especially if the object message queues are lock-free. However, one of the keys to such an architecture is making sure that there are no shared sub-allocators being used by the RTL for memory allocation.