Those are kind of fundamental to multicore / multithreaded CPUs, not just Intel. If I have many tasks running on the same CPU, tasks can interact in complex way

Those are kind of fundamental to multicore / multithreaded CPUs, not just Intel. If I have many tasks running on the same CPU, tasks can interact in complex ways. That can leak traces of information, and a clever enough person can pry that tincan open. Not much one can do about it, other than running untrusted tasks in a sandbox with very well-controlled performance. That means slow performance.