Does not seem practical to me. A server accepting TLS connections would have almost always some thread doing “frequency fenced” code so the CPU would always be

Does not seem practical to me. A server accepting TLS connections would have almost always some thread doing “frequency fenced” code so the CPU would always be frequency locked. It's much more practical to just disable Turbo-boost. A more simpler mitigation is just add noise, perform random computations so the whole algorithm is constant time + random time. Greatly increases the difficulty of gathering timing data.