I don't think memory bandwidth is the limiting factor for a modern CPU. If instruction fetching was not only consuming most bandwidth but also dominated it, the

I don't think memory bandwidth is the limiting factor for a modern CPU. If instruction fetching was not only consuming most bandwidth but also dominated it, then there would be little benefit to SIMD if you could just do multiple instructions instead as the bandwidth is taken up anyways (notably in multicore systems). That plus to my knowledge, there is no single core performance difference at same clock between a 4-core and 12-core CPU in AMD CPUs, which would be the case if instruction fetching is maxing out memory bandwidth.