Yes, we know that the title of this week’s post sounds a lot like two previous posts. We wanted to link together the two threads from those posts into a single message that we believe reflects what is happening right now in the world of complex chips. This is a short summary in line with the short week due to the Thanksgiving holiday here in the United States. The line of argument is straightforward:

• Large chips are adding embedded processors to implement complex functionality while retaining flexibility
• Single-processor chips are adding multiprocessor clusters to get better performance at a given process node
• Multiprocessor chips are using shared memory for effective data transfer and interprocess communication
• Neighbor-connected processor arrays are moving to shared memory to reduce cross-chip data latency
• Multiprocessor designs are adding caches to reduce memory access time and bypass memory bottlenecks
• Multiprocessors with caches require coherency in order to ensure that the right data is always accessed

While most of these statements are not universally true, they reflect a significant sea change that we see every day when discussing current and future projects with our customers.

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Last week’s post was addressed primarily to those of you who are already designing SoCs. We made the point that more and more SoCs have multiple processors, either homogenous or heterogeneous, and that most or all of those processors do or will have caches. This led to the main conclusions of the post, that multi-processor cache coherency is necessary for most SoCs, and therefore that coherency is now a problem extending beyond CPU developers to many chip-level verification teams.

But what if you don’t have embedded processors in your design? There’s a clear sense emerging in the industry that more and more types of chips are becoming multi-processor SoCs, and most of these will require cache coherency for the CPU clusters and beyond. In this post we’ll describe the trends we see, based in part on what we learned at the recent Linley Processor Conference in Santa Clara. The world as we know it is changing rapidly, offering more challenges for verification teams but more opportunities for us to help.

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