meltdown / rowhammer are pretty fundamental design problems, spectre is even a pretty fundamental logic problem. It hasn't been comprehensively fixed in HW and

meltdown / rowhammer are pretty fundamental design problems, spectre is even a pretty fundamental logic problem. It hasn't been comprehensively fixed in HW and probably will never be because it directly contradicts the need for reasonable perf on multicore CPUs (at the intersection between speculative/OOO execution and cache coherency, and both are needed for reasonable perfs). Rowhammer is also hard to comprehensively fix for physics reasons, but hopefully some dedicated mitigations plus ECC are good enough for not ultra-critical applications; some people think more could be done that could practically fix it, but I don't know if they have managed to convince the industry (and get some value from their patents in the process). So of the three, only meltdown could be really fixed by a quick iteration of processor design (and it is also workaround by the OS on old affected models, at a performance cost)