SoC design: When is a network-on-chip (NoC) not enough?

By Guillaume Boillet, Arteris IP
EDN (June 7, 2023)

In the not-so-distant past, system-on-chip (SoC) devices were relatively simple compared to today’s offerings. Early SoCs typically consisted of 10 to 20 intellectual property (IP) blocks, each generally composed of around 10,000 to 50,000 logic gates. Most of these IPs, including the processor and peripheral functions, were licensed from third-party vendors. Developers normally created only one or two IPs containing the “secret sauce” that differentiated their SoC from other competitive offerings.

A classic bus architecture approach was used when interconnects requiring a limited number of IPs to communicate with each other were relatively simple. Designers responsible for very few initiator IPs—which orchestrated the data transaction requests combined with multiple target IPs that responded to those requests—used this method.

As the number and size of IPs increased and they assumed the role of initiators, it became necessary to adopt more sophisticated interconnect architectures in the form of crossbar switches. A crossbar switch was advantageous since it allowed any initiator IP to talk to any target IP. However, as the capacity and complexity of SoCs continued to increase, crossbar switches posed challenges such as routing congestion, excessive use of silicon die area, and power consumption.

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