Case Study: Chip Design Costs Make Processor Core Choice Paramount

Submitted by BDTI on Thu, 03/22/2012 - 05:00

As we’ve all heard, the cost of creating a custom chip has skyrocketed. Still, there are applications where a custom chip is justified—usually by specialized, demanding technical requirements. Today, custom chips often incorporate multiple processor cores.  The choice of a licensable processor core is among the first decisions that a design team makes, and may be the decision that they live with the longest: the hassles of porting software from one processor architecture to another mean that once a company has selected a core, it is likely to stick with that core (or compatible successors) for multiple generations of chip designs. Hence, the core selection decision must be a good one.  But, typically, the decision also has to be made very quickly: the design team is under pressure to get the design underway, and can’t afford to spend months evaluating cores.

Consider a team working on a miniature, battery-powered medical device. Such a product requires very low power consumption, of course, so the energy efficiency of the processor core will be a primary concern.  But determining which processor core will result in the most energy efficient chips can be tricky; power data provided by core vendors is all over the map in terms of conditions and assumptions.  The situation is further complicated by the different types of cores available—including CPU, MCU, DSP, and DSC cores—and by options that combine multiple cores in various ways.

Ease of software development will likely be another key consideration, since medical devices typically run lots of proprietary software (as opposed to off-the-shelf software modules).  Here again, it can be tough to quickly and accurately judge the quality of the software development tools associated with a processor core. 

BDTI regularly assists design teams in the evaluation and selection of processor cores. One key asset that BDTI brings to these projects is its broad knowledge of current core offerings.  BDTI receives frequent briefings from core vendors, and often evaluates cores in detail, including hands-on benchmarking.  As a result, BDTI often knows about unannounced cores that are under development, and can seek permission from the core vendor to disclose the new core to a chip design team that may find it attractive, helping to ensure that the chip design team finds the core that best meets its needs.

To understand in more detail how BDTI helps chip designers, consider a recent example project. An equipment company was setting out to design a SoC to meet the performance requirements of an ultra-low-power medical device. The chip design team had experience with a number of licensable processor cores, but decided to engage BDTI’s consulting services to ensure that it had not overlooked strong core candidates and that its evaluation was as accurate as possible. The company recognized that the choice of a core would significantly impact the success of its chip, and that it would live with the consequences of the choice for a long time.

BDTI was able to develop a list of candidate processor cores in one week. The list included 15 cores—some of which the client had not previously been aware of. Subsequently, BDTI narrowed the list of choices for the client based on the most important selection attribute–low power. Short of actually building a test chip, it’s incredibly tough to compare the power consumption of licensable processor cores. Many factors impact core power consumption, including the type of code running on the processor, temperature, the process technology in which the chip is manufactured, the choice of cell library, and synthesis process optimizations used in the chip design.

Over the past 15 years, BDTI has evaluated numerous licensable processor cores.  In the course of this work, BDTI has developed a number of tools for this kind of analysis.  For example, BDTI has created a methodology for obtaining reliable, apples-to-apples comparison of processor core power consumption.  The BDTI methodology relies on a standardized set of conditions for evaluating core power consumption. In cases where vendors provide data that does not comply with BDTI’s conditions, BDTI adjusts the vendor-supplied data to account for differing conditions and enable apples-to-apples comparisons.

In the case of the medical equipment manufacturer, BDTI used this methodology to quickly develop a power consumption comparison of the 15 candidate processor cores.  Based on this comparison, BDTI selected a handful of the most promising candidates for additional analysis, including considerations of ease-of-use and product maturity. Levering its existing knowledge, evaluation methodology, and contacts, BDTI was able to deliver a solid set of recommendations to the chip design team in just four weeks.  This enabled the team to keep to its aggressive chip design schedule, without compromising on the quality of its core-selection decision.

BDTI can help you choose the right processor for your next project. Learn how by contacting Jeremy Giddings at +1 (925) 954 1411 or

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