Considerations For Choosing The Right Low-Power Tools

By Cheryl Ajluni
Regardless of what you are designing these days, one fact holds true: Your design is only as good as the design tools you use.

Gone are the days when a design could be done on the back of napkin. Today, engineers require a complex ecosystem of interworking tools to guide them through the complex design flow. This is especially true when it comes to low-power design, as its complexity now permeates every aspect of the design flow, creating challenges that threaten to derail design closure at every turn. Here, automated design tools can play a key role in speeding the design process, selecting optimal low-power architecture and ensuring design closure.

The problem, of course, is low-power or “power-aware” design tools and flows are still in their infancy—a fact that poses a bit of a dilemma for designers. Not only do they need to figure out what type of power management and low-power design techniques to employ, but they must also determine which tool vendors support those techniques. Then they have to evaluate the possible tool options and make a selection. This can be a stressful and time-consuming process, especially when you consider the decision is critical to the success of any design project and, for that matter, to a company’s overall success and vitality. While there are no hard and fast rules for selecting the right tool, or the right vendor, there are a number of considerations—over and above a tool’s verified functionality—that engineers can use to help simplify their decision. Those considerations include:

• Cost. A tool’s actual cost and its available pricing options are important considerations when evaluating a design tool. Of course, a tool’s true cost is also impacted by its learning curve and overall reliability—both of which can affect downtime—and therefore must also be considered prior to making a tool purchase.
• Speed. While it may not always seem like a key consideration, how fast a tool operates can directly impact the designer’s time-to-market schedule as well as overall design costs and therefore should not be overlooked. Was it designed for multicore processors, or simply updated to take advantage of them?
• Support for Industry Standards. Using a tool built to emerging low-power industry standards, such as the Common Power Format (Cadence and Magma) or the Unified Power Format (Synopsys, Mentor and Magma), ensures that it will interoperate with a range of other design tools and flows. It is also smart to select a tool that can be used within industry-accepted reference flows such as the power-aware reference flow recommended by the Low-Power Coalition (LPC) of Si2 or Accellera, respectively.
• Ease of Use. Is the design tool easy to use? Does it require special training or low-power design expertise? Does it make you more efficient or productive? Does it support multi-language user interfaces for globally disperse design team members and are the user interfaces familiar? Is it easy to deploy, administer and maintain? Does it integrate well with other low-power design tools and design flows? All of these factors should be carefully considered during a tool’s evaluation.
• Flexibility. Is the tool flexible enough to accommodate changes in technology and can it adapt to changing business conditions—an especially critical question given the current state of the global economy? Can it support the needs of a globally-disperse design team with features like revision control and policy control for IP management?
• Customer Support. How responsive a tool vendor is to the designer’s support needs can be vitally important to the success or failure of your low-power design. Does the vendor provide quality documentation, training when needed or on site technical support? Does the vendor have proven expertise in low-power design? Such expertise may prove invaluable if you find yourself facing a difficult low-power design problem.
• Vendor Credibility. Don’t forget to verify the tool vendor’s reputation with other designers. If they have had trouble with the vendor, then chances are good that you will, too.

Design Tool Options
Despite the fact that low-power design tools and flows are still relatively new, there are a number of options to choose from. A sampling of these tools includes the following:

• Catapult C Synthesis and SpyGlass-Power, from Mentor Graphics and Atrenta, respectively. SpyGlass-Power is an RTL power estimation and reduction tool that is used to automate multi-level clock gating. Catapult is a high-level synthesis tool that offers a fast path to verified RTL from pure C++. New low-power optimizations enable the tool to thoroughly analyze a design to determine gateable clocks and build the appropriate logic. An interface now exists between these two tools that allows RTL output from Catapult to be handed off to SpyGlass-Power. Static and dynamic power estimates from SpyGlass-Power can then be fed back into Catapult C.
• Eclypse Low Power Solution from Synopsys. Eclypse is an integrated flow of tools, intellectual property and methodologies that allows designers to include everything from MTCMOS power gating, multiple voltages, dynamic voltage and frequency scaling. The goal is to dramatically simplify design and the increasingly complex verification portion of that design. Eclypse also includes clock gating, low-power clock tree synthesis and leakage power recovery. As you might expect, it includes UPF support, as well as support for the Low-Power Methodology Manual created by Synopsys and ARM.
• Cadence Low-Power Solution from Cadence Design Systems. Cadence’s Low-Power Solution is a CPF-enabled design-to-signoff methodology that makes it easy to incorporate low-power design techniques in advanced SoCs. It includes tools like the InCyte Chip Estimator for chip planning, Encounter RTL Compiler for logic synthesis, Encounter Conformal Low Power for structural, functional and equivalence checking; the Encounter Digital Implementation System for physical implementation, the Encounter Power System for power rail analysis, and Incisive Formal Verifier for formal property checking (Figure 1).

Figure 1. The Encounter Power System solution accelerates power optimization and signoff with a unified timing and power database. It can be used by front-end logic designers seeking high-quality early power and rail analysis, as well as by back-end physical designers looking for comprehensive signoff analysis and silicon-correlation.

• PowerPro CG and PowerPro MG, from Calypto Design Systems (www.calypto.com). The PowerPro CG tool reduces power by implementing sequential clock gating logic in the non-memory portions of an RTL design. PowerPro MG is a memory gating tool that automatically generates power-optimized RTL by taking advantage of the low-power modes available in on-chip memories. It works with PowerPro CG to produce the lowest power design possible.
• Talus Implementation System, from Magma. The Talus implementation system provides a fully integrated RTL-to-GDSII flow for high-performance, high-complexity, low-power nanometer designs. Talus Design and Talus Vortex are key tools in the system. Talus Design is a full-chip synthesis environment, while Talus Vortex is a physical design environment. Another tool, Talus Power Pro, works in conjunction with Talus Design and Talus Vortex to enable optimal power management throughout the flow.
• PowerArtist-XP and PowerTheater, from Sequence Design (now part of Apache). PowerArtist-XP is an RTL Design For Power (DFP) platform that features fully-integrated advanced analysis and automatic reduction (Figure 2). Using it, designers can achieve a 10 to 60 percent or more power savings. PowerTheater is a solution for RTL power analysis.

Figure 2. PowerArtist-XP enables designers to make intelligent design decisions that maximize power savings while minimizing design impact.

The Bottom Line
While designing for low power remains a difficult and complex challenge these days, appropriate use of low-power (power-aware) design tools can help simplify the process. Such tools will only become better and easier to use with time. Of course, selecting the right tool or tools is absolutely critical to a successful low-power design, perhaps just as critical as determining which low-power design and power management techniques to implement. While there is no set criterion to follow when making this decision, the considerations outlined above can serve as a guide in helping to make your decision that much easier.