Shared bypass bus structure
A shared bypass bus structure for low-latency coherency controller access in a coherent scalable switch. In a coherent scalable switch with multiple coherent interconnect ports, distributed coherency control structures, and a crossbar interface between them, a shared bypass bus permits data transfer between the coherent interconnect ports and the coherency control structures while bypassing the crossbar interface. Some embodiments may comprise scalable switches to support one or more sets of processors with substantially independent snoop or cache coherency paths or arrangements.
1. An apparatus, comprising:
a bypass bus structure coupled between a first coherent interconnect port and a coherency control structure to transmit data for a cache coherency operation substantially independent of transmission with a crossbar structure coupled to the first coherent interconnect port; and
an arbitrator coupled with the bypass bus structure to coordinate transmission of the data between the first coherent interconnect port and the coherency control structure.
2. The apparatus of claim 1 , wherein the bypass bus structure comprises a multiplexing structure to transmit more than one transaction on the bypass bus structure.
3. The apparatus of claim 1 , wherein the bypass bus structure comprises an incoming bus and an outgoing bus.
4. The apparatus of claim 1 , wherein the first coherent interconnect port is coupled with a downbound snoop path and a second coherent interconnect port is coupled with a scalable node controller.
5. The apparatus of claim 1 , wherein the bypass bus structure comprises a remote bus structure and a local bus structure.