No not all cpus are affected, not by a very long shot. Only ones that have speculative execution (through a vulnerable cache design). And from what they are saying/implying it has to be more than just a little branch prediction/prefetch, meaning it needs more fetching than that. I cant see this core falling into that category. But will see I guess. If you dont have an mmu/cache then you are certainly not vulnerable to this category of problem.