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Can one processor rule them all?

02 Nov 2012  | Robert Cravotta

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Similar to Middle-earth in The Lord of the Rings, the ecosystem for embedded and computing systems is home to a diverse population. Instead of elves, dwarves, Hobbits, and humans, all manner of processor architectures inhabit the compute and embedded-processing ecosystem. The various microprocessors, digital signal processors, and microcontrollers implement different optimization choices to meet system designers' myriad design requirements.

That analogy occurred to me as I read a number of recent articles and public online discussions. Collectively, they ask two questions that implicitly share the same underlying architecture: Are 8bit processors dying, and is ARM winning the processor war? The articles and discussions all suggest that the ARM architecture will be the one to put the final nail in the coffin of smaller-bit-width microcontrollers and will possibly even crowd out other 32bit microprocessors in other application spaces. In this rapidly evolving ecosystem, can the ARM architecture become the one to rule them all?

The analogy serves only as an illustration of the common, implied architectural theme running through these questions and the accompanying discussions; it is not meant to be a statement about the discussed processor architectures or about the ecosystem companies that support them. At least for me, however, the analogy provides a visual image that captures the almost palpable expectation that a single processor architecture might finally deal the death blow to 8- and 16bit architectures one day soon, as well as possibly dominate traditional applications for 32bit and larger microprocessors.

Is such a consolidation of processing architectures possible? Is it even desirable?

Let's begin this exercise by stipulating that with regard to cost, workload capacity, and energy consumption, a specific 32bit processor has achieved or surpassed parity with a specific 8bit processor that is being used for a specifically defined workload. The point of this precisely worded stipulation, beyond avoiding data-sheet debates, is to emphasize that the replacement of any processor with another is performed on a case-by-case basis that distinguishes between explicit alternatives in the context of an explicit workload (expected or already implemented). When the new alternative is superior to the incumbent implementation, there is an opportunity for a migration to the new alternative.

Migrating a workload to an alternative device as part of the life cycle of both the workload and the available processing options, however, is not the same as migrating to an alternative expressly because the incumbent processor width or architectural implementation has become obsolete.

As an example, consider the analogous, long-debated statement that FPGAs will drive DSPs to obsolescence. It has been repeatedly demonstrated that FPGAs can perform arbitrarily wide signal-processing tasks more quickly and efficiently than dedicated DSPs. For a given workload, however, a specific processor that incorporates the optimal type and number of execution units to implement that specific workload can negate an FPGA's performance and efficiency advantage.

In fact, a realistic life-cycle scenario for contemporary signal-processing workloads could initially see a workload under development implemented as software on a high-performance microprocessor or DSP in simulations and prototypes. As the volatility and uncertainty of the workload implementation stabilized, the developers would migrate it to an FPGA to optimize performance, price, and energy consumption. Once designers adopted the workload for a large number of high-volume designs, a semiconductor company might decide to produce a specialized processor or coprocessor integrated with a microprocessor or DSP that targeted the specific workload; that development, in turn, would justify yet another migration of the workload, this time to a software implementation on said device. None of those migrations would be cause for concern that microprocessors, FPGAs, or DSPs were becoming obsolete.

About the author
Robert Cravotta is principal analyst at Embedded Insights Inc.

To download the PDF version of this article, click here.




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