Earlier quoted context omitted.
Yeah TDP is calculated differently for Intel and AMD, usually to make Intel look better. It makes it harder to compare because hardware components are going to be different (e.g. different mobo, different memory, etc) but they should measure wattage out the wall.
Intel's is roughly "the thermal dissipation required to maintain base clock speeds indefinitely without thermal throttling". AMD's is roughly "the thermal dissipation required for all-core turbo indefinitely". In recent generations (since AMD's Zen architecture), AMD is much closer in testing to their published numbers than Intel is. It is important to note that this is a thermal specification, rather than a power co…
Nitpick warning - I assume you mean that they are passively cooled in free air. They are still emitting heat into their environment. If you stuck such a processor into a perfectly insulated container, it would eventually overheat and throttle down. So it's really only fair to call them 0 TDP if you ignore the base "free" cooling. You could make the same assumption about power if you just stuck a solar panel on top (like a calculator processor) and then ignored that power input.