1. Field of the Invention
The present invention relates to ports for a shared memory node, and more particularly, to scalable ports for connecting two or more nodes together.
2. Description of the Related Art
Conventional scalable multiprocessors consist of multiple nodes that are connected together using an interconnect system. Each node consists of a processor, dynamic random access memory (DRAM), and an input/output (I/O) device. The processor, DRAM, and I/O device couple with a bus. A single chipset also couples with the bus and controls interactions between all of the components.
The single chipset also couples with a conventional interconnect port. A conventional interconnect port is an external interface that allows for physically connecting nodes together in an interconnect system. Connecting multiple nodes together may allow for creation of a shared memory system. An example of a shared memory system is a Cache Coherent, Non-Uniform Memory Access (CC-NUMA) architecture.
In an interconnect system, to connect one node to another node requires an interconnect port. Where there are only two nodes, the interconnect port is optimized for communication between these two nodes only. A dedicated interconnect port in two node systems is more popular and more commonly in use than systems having three or more nodes. However, because the interconnect port is also dedicated for such two node systems, the interconnect port is not scalable beyond two nodes.
Interconnecting more than two nodes requires adding additional hardware between the interconnect port and each additional node. This additional hardware is used to scale the ports. The additional hardware also increases the overall cost of the system. Further, the additional hardware requires additional system space making it less suitable for limited space environments and applications. The additional hardware also increases the number of signal delay points that, in turn, causes a decrease in overall system performance. The additional hardware and the problems it introduces is another reason why such conventional interconnect ports are not desirable for systems with only two nodes.
In summary, some problems with conventional interconnect systems are that there may be a need for up to three different types of interconnect ports when adding or removing nodes from the interconnect system. If there is only one node, no interconnect port is needed. If there are two nodes, a non-scalable interconnect port is needed. If there are three or more nodes, a scalable interconnect port is needed. However, this scalable interconnect port is inefficient for two node systems.
Therefore, there is a need for an interconnect port that (1) is scalable, (2) has high performance in systems having three or more nodes, as well as two node systems, and (3) does not increase system costs when additional nodes are added to the system.