That's not quite true. Datasheets provided by the CPU manufacturer always (at least as far as I have ever seen) list the worst-case scenario for thermal output, which is <i>very</i> important for heat sink designers (to know if they support the CPU or not) and system builders (to know what heat sink they'll need). Generally the heat will be better than that since it is a worst-case scenario, but it is at least a good guideline.Heat is not shown, never will because it varies, no CPU chip is the same.