The Silicon Integration Initiative (Si2) Conference Oct. 20 provided an ambitious new roadmap for low power standards. Presentations described the current Common Power Format (CPF) 2.0 release, steps towards interoperability with IEEE 1801 (Universal Power Format, UPF), a new approach to power modeling, and the need for system-level power modeling including the impact of software. These presentations updated the work of the Si2 Low Power Coalition (LPC).
This blog post takes a brief look at the following presentations:
- Qi Wang, technical marketing group director for low power solutions at Cadence and vice-chair of the LPC, discussed CPF 2.0 and steps towards IEEE 1801 interoperability.
- David Hathaway, senior technical staff member of IBM and LPC TSG (technical steering group) chair, described recent work in "power contributor modeling."
- Steve Schulz, Si2 president, gave a rousing call to action for getting to work on system-level power modeling - now.
These were just a few of the 15 presentations during the day-long conference, which also updated Si2's work on standards for process design kits (PDKs), design for manufacturability (DFM), and OpenAccess. Copies of presentation slides will be available on the Si2 web site this week.
At the conference, Schulz also presented Si2 Distinguished Service Awards to both Wang and Hathaway. Wang was honored for "many years of successful support and guidance of the LPC and the format working group," as well as his recent work in the IEEE P1801 working group. Hathaway was honored for his years of service in the LPC technical steering group as well as the working groups he's led.
CPF 2.0 and Interoperability with IEEE 1801
Wang noted some key milestones in the LPC Format Working Group, including:
- CPF 2.0 released March 2011
- CPF 2.0 tutorial webinar in May 2011
- OpenLPM (Low Power Methodology) contributed to IEEE 1801 in June 2011
- Interoperability Guide update approved by LPC in October 2011
He discussed CPF 2.0 highlights including macro-modeling improvements, new low-power IP blocks, and simulation enhancements. Modeling has been improved for low-power mixed-signal elements such as voltage regulators and analog ports. New low-power IP includes power and ground level shifters, bypass level shifters, and clamp cells for isolation. New verification features allow more control and functionality in simulation and emulation.
Much of the current focus, however, is on CPF interoperability with IEEE 1801. "We have to realize that even though these two formats are similar, there are fundamental differences," Wang said. "There are key methodology differences. Without resolving them there is no point in talking about format convergence."
CPF 2.0 added some new features to make interoperability easier. These include a more flexible power domain specification, a functional model definition, a hierarchical flow that allows virtual output/input ports, and state retention rule enhancements. Beyond CPF 2.0, OpenLPM is a converged power methodology designed to facilitate complete interoperability between CPF and IEEE 1801. It emphasizes the 1801 supply-set methodology over the older UPF 1.0 power/ground net-based methodology, deprecates incompatible UPF 1.0 constructs and methodologies, and extends 1801 to include commonly used CPF features.
The next CPF release, CPF 2.1, will have additional interoperability features and will have "potential extensions to enable system-level power intent specification," Wang said.
Power Contributor Modeling
Hathaway introduced some of the work done by the LPC Modeling Working Group in "power contributor modeling," particularly as it applies to leakage. He first noted that leakage power is highly variable across a PVT (process, voltage, temperature) range. Designers may want to do some early analysis when you don't know what the voltage is. What's needed is a PVT-independent way of representing the leakage.
The best approach, Hathaway said, is "don't put power in a power model, put descriptions of contributors into the power model." (A contributor could be something like channel leakage of devices, or gate leakage). The idea is to get a small set of contributors, each of which can be simulated - as opposed to the huge number of states that a conventional modeling approach would require.
Many design flows do something similar, Hathaway said - such as estimating leakage by looking at total device width. The LPC is looking for a standardized approach, but not necessarily a new standard; the working group is working on a proposal that would enhance the Liberty library syntax.
Moving Up to Software
Schulz' talk was titled "The Next Frontier in EDA Standards," and his discussion of the "next frontier" was all about power. He noted first that power is a multi-dimensional problem because it has so many interactions and tradeoffs with other concerns. Invoking the 80/20 rule, he said that the "greatest opportunity" to reduce power is "at the higher levels, before you've made some of the committed decisions that lock you into a certain tradeoff."
"Software is a fundamental and primary driver of dynamic power consumption, and that's something we're going to have to take seriously as an industry," Schulz said. He noted, however, that "you're not going to simulate every detail of an application, so what we have to do is think about a smarter way of capturing the most important parts of that information, and communicating that back from the software world into the [hardware] world we live in."
What's needed, he said, is a system-level specification of power intent, and "part of that is already in the early stages for the next revision of CPF, because the idea is to move up to the ESL [electronic system level] stage. That is very important work and we need input, we need help in figuring out the smart way to do that."
"I don't know when you think this kind of capability will be needed in the industry, but if you think it's less than 5 or 6 years out, then we're late," Schulz concluded. "We need to get started now."
For another report on the Si2 Conference, see my previous post on DFM standards.
Related blog post from 2010
Si2 Speakers: EDA Standards Must Address Systems, Software