A processing apparatus comprising: a bus; a first processor connected to the bus and configured to communicate over the bus according to a bus protocol; a second, multithread processor; and an inter-thread interconnect based on a system of channels. The apparatus also comprises an interface between the bus and the inter-thread interconnect, comprising a bus side implementing the bus protocol and an interconnect side for interfacing with the system of channels. The first processor is thereby operable to communicate with a designated one of said threads via the bus and a respective channel of the inter-thread interconnect.