Apparatus and method for a cache coherent shared memory multiprocessing system

• US 6,457,087 B1
• Filed: 05/12/2000
• Issued: 09/24/2002
• Est. Priority Date: 12/07/1997
• Status: Expired due to Term

• Current Assignee: Intellectual Ventures II LLC (Intellectual Ventures LLC), HotRail, Inc. (Synaptics Incorporated)
• Original Assignee: Conexant Systems Incorporated (Synaptics Incorporated)
• Inventors: Fu, Daniel D.
• Primary Examiner(s): Wong, Peter
• Assistant Examiner(s): VO, TIM T
• Application Number:
  US09/570,832
• Time in Patent Office: 865 Days
• Field of Search: 710/100, 710/129, 710/30, 710/52, 711/131, 711/110, 711/149, 709/233
• US Class Current: 710/305
• CPC Class Codes: G06F 12/0813 with a network or matrix configuration
• CPC Class Codes: G06F 12/0822 Copy directories local copy tags for implementing a bus snooping protocol G06F12/0831

Abstract

The system and method for operating a cache-coherent shared-memory multiprocessing system is disclosed. The system includes a number of devices including processors, a main memory, and I/O devices. Each device is connected by means of a dedicated point-to-point connection or channel to a flow control unit (FCU). The FCU controls the exchange of data between each device in the system by providing a communication path between two devices connected to the FCU. The FCU includes a snoop signal path for processing transactions affecting cacheable memory and a network of signal paths that are used to transfer data between devices. Each signal path can operate concurrently thereby providing the system with the capability of processing multiple data transactions simultaneously.

Claims

1. A flow control unit for use with a plurality of processing devices and a memory, the flow control unit comprising:

first point-to-point interfaces configured for coupling to first point-to-point connections to the processing devices;

second point-to-point interfaces configured for coupling to second point-to-point connections to the memory;

first signal paths coupled to the first point-to-point interfaces;

second signal paths coupled to the second point-to-point interfaces;

node switches coupled to the first signal paths and the second signal paths and configured to couple selected ones of the first signal paths with selected ones of the second signal paths; and

a controller coupled to the node switches and configured to control the node switches to couple the selected ones of the first signal paths to the selected ones of the second signal paths to establish selected communication paths for data transfer transactions between individual ones of the processing devices and the memory through the first point-to-point connections, the first point-to-point interfaces, the first signal paths, the node switches, the second signal paths, the second point-to-point interfaces, and the second point-to-point connections.

2. The flow control unit of claim 1 wherein the processing devices each have a cache that is shared by the processing devices and the flow control is configured to maintain cache coherency.

3. The flow control unit of claim 1 wherein at least some of the second signal paths are associated with a particular set of locations in the memory.

4. The flow control unit of claim 1 wherein at least some of the first signal paths are associated with particular ones of the processing devices.

5. The flow control unit of claim 1 further comprising:

third point-to-point interfaces and the first point-to-point connections wherein the processing devices are coupled to the third point-to-point interfaces, the third point-to-point interfaces are coupled to the first point-to-point connections, and the first point-to-point connections are coupled to the first point-to-point interfaces;

fourth point-to-point interfaces and the second point-to-point connections wherein the memory is coupled to the fourth point-to-point interfaces, the fourth point-to-point interfaces are coupled to the second point-to-point connections, and the second point-to-point connections are coupled to the second point-to-point interfaces; and

wherein the controller is configured to control the node switches to establish the selected communication paths through the third point-to-point interfaces, the first point-to-point connections, the first point-to-point interfaces, the first signal paths, the node switches, the second signal paths, the second point-to-point interfaces, the second point-to-point connections, and the fourth point-to-point interfaces.

6. The flow control unit of claim 1 wherein the first point-to-point connections are also to an I/O device and the controller is configured to control the node switches to couple the selected ones of the first signal paths to the selected ones of the second signal paths to establish selected communication paths for data transfer transactions between the I/O device and the memory through the first point-to-point connections, the first point-to-point interfaces, the first signal paths, the node switches, the second signal paths, the second point-to-point interfaces, and the second point-to-point connections.