An apparatus comprising: a fabric block including circuitry to support a plurality of coherent protocols; an agent block including circuitry to support at least one of the plurality of coherent protocols from the fabric block; and an interface between the fabric block and the agent block, including: a request physical channel (330, 350) to carry address and protocol level command information associated with requests from the agent block or the fabric block; a response physical channel (335, 355) to carry responses to the requests from the agent block or the fabric block; a data physical channel (325, 345) to carry data transfers from the agent block or the fabric block; and a global physical channel (320, 340) to carry global control signals that apply to the request physical channel (330, 350), the response physical channel (335, 355), and the data physical channel (325, 345), wherein the plurality of coherent protocols are tunneled on the interface; and wherein the request physical channel (330, 350), the response physical channel (335, 355), the data physical channel (325, 345), and the global physical channel (320, 340) each includes a respective set of wires, each set comprising one or more wires. a fabric block including circuitry to support a plurality of coherent protocols; an agent block including circuitry to support at least one of the plurality of coherent protocols from the fabric block; and an interface between the fabric block and the agent block, including: a request physical channel (330, 350) to carry address and protocol level command information associated with requests from the agent block or the fabric block; a response physical channel (335, 355) to carry responses to the requests from the agent block or the fabric block; a data physical channel (325, 345) to carry data transfers from the agent block or the fabric block; and a global physical channel (320, 340) to carry global control signals that apply to the request physical channel (330, 350), the response physical channel (335, 355), and the data physical channel (325, 345), wherein the plurality of coherent protocols are tunneled on the interface; and wherein the request physical channel (330, 350), the response physical channel (335, 355), the data physical channel (325, 345), and the global physical channel (320, 340) each includes a respective set of wires, each set comprising one or more wires. a request physical channel (330, 350) to carry address and protocol level command information associated with requests from the agent block or the fabric block; a response physical channel (335, 355) to carry responses to the requests from the agent block or the fabric block; a data physical channel (325, 345) to carry data transfers from the agent block or the fabric block; and a global physical channel (320, 340) to carry global control signals that apply to the request physical channel (330, 350), the response physical channel (335, 355), and the data physical channel (325, 345), wherein the plurality of coherent protocols are tunneled on the interface; and wherein the request physical channel (330, 350), the response physical channel (335, 355), the data physical channel (325, 345), and the global physical channel (320, 340) each includes a respective set of wires, each set comprising one or more wires.