1. A method comprising: responsive to detecting a read request referencing a specific memory address from a first entity that misses in a core cache of the first entity: sending an order-marker corresponding to the read request to the first entity on a first channel; sending a fill corresponding to the read request to the first entity on a second channel; and responsive to detecting an update request from a second entity, ordered after the read request, referencing the specific memory address, the update request received in a second level tag directory of a multi-level tag directory hierarchy via a first level tag directory of the multi-level tag directory hierarchy: sending, from the second level tag directory, a second order-marker to the second entity, via the first level tag directory; sending update data packets on the first channel to all non-last accessor entities having copies of the specific memory address; sending, from the second level tag directory, a probe update data packet on the first channel to a last accessor entity if the last accessor entity is different than the second entity and changing a last accessor state of an entry of the second level tag directory to point to the second entity; and sending an update acknowledgement (upd_ack) to the second entity.