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Configurable Thoughts
  • About

    This blog is about everything to do with microprocessors. While we discuss architecture, tools, best practices, new innovations, performance, and system implementation, we also look at software, applications, and the larger industry trends. The processor market is a fascinating place today, and even though it has been around for more than 30 years, it is in many ways just getting started. We would love to hear from you on our blog posts, and please don't hesitate to let us know if you think we are wrong — it does happen occasionally.
  • About the Authors

    Michael Thompson

    At the age of 10 Mike begged his father to get him a computer. Never mind that at the time computers were the size of a large office and cost millions of dollars. Yes, Mike is no spring chicken and he didn’t get the computer, although his father did give him an abacus telling him that it would enable him to use the computer that he already had between his ears, which was not appreciated. Whether it was due to the trauma that resulted from using an abacus or just Mike’s love of anything electronic he has spent the last 30 years or so designing, building, and programming computers, microprocessors, and microcontrollers and developing applications that run on them. And his fascination continues with the definition of new processors and architectures in his search for the holy grail of computing: infinite performance at zero power consumption. Statistically speaking he is convinced it is just a matter of time.

    Allen Watson

    Allen started in the ‘semiconductor IP industry’ before it was called the ‘semiconductor IP industry’. Back then, it was about ‘megafunctions’, ‘megablocks’ or MegaMacros™ (as trademarked by the pioneering UK IP company Allen was with… no, not that UK company). The biggest of these ‘mega’ things was an 8051! Today, of course, IP blocks are much larger and much more complex. And, it’s about the software, as well as the hardware. It’s also about working with a set of partners, sometimes called an ecosystem or community. Allen has been doing that for many years and is enjoying working with old and new friends on the ARC processor ecosystem.

Does Size Matter?

Posted by Mike Thompson on November 26th, 2012

Well of course that depends on what you are talking about. In the world of microprocessors size does matter. Not only does size equate to cost, but also to power consumption. Depending on the design that you are doing both can be major considerations. There can also be size considerations for the amount of memory that will be used with the processor making code density a critical parameter. If the only thing that you care about in a design is performance then size maybe doesn’t matter, but then again maybe it does. It used to be that I would have customers tell me that performance is all that mattered. I don’t hear that so much anymore – in fact it is rare.

For processors that are designed for embedded and deeply embedded applications size and power more often than not are the main requirements. That a processor can run at 500 MHz doesn’t matter so much if you are only planning on clocking it at 10 MHz, but size gets really important if the application is a sensor and you are planning to put it in a 2×2 mm package. As small as that is power consumption can be even more challenging. I have seen specifications for sensors where 100uW is the total power available for the whole sensor. When you consider that this level of power could easily be consumed by leakage it becomes apparent that the total sensor implementation has to be very small. This takes a special breed of microprocessors that are designed from the ground up to be implemented to minimum size and power, but also with excellent instruction performance to minimize the memory requirements.

With this in mind Synopsys developed the EM family of 32-bit processors. Designed for sensor and embedded control applications the cores start at fewer than 10K gates and can be quickly configured to a specific application, so that no gates are wasted. This is especially important at the older process nodes where many of the sensor and control applications are being implemented and each additional gate takes a lot more area and power.

The EM processor family has also been designed to reduce the memory footprint offering 20% better code density, which reduces power consumption and leakage. It is not unusual for the memory that is attached to a processor to take more area than the processor. A 20% reduction in the amount of memory needed for an application can be very significant, especially when area and power are limited.

Performance is still important in many applications, but more and more power and size are dominating processor selection criteria. Whether it is to increase battery life or reduce the operating cost of an application the size of a processor and the memory that it requires matters, and this will be increasingly true as we move forward.