The new IEEE 1801-2013 Standard for Design and Verification of Low Power Integrated Circuits, to use its full name, is much more than an incremental release of the Unified Power Format (UPF). Ratified by the IEEE Standards Association on March 6th, the IEEE has just announced its publication. The new standard represents significant progress towards methodology convergence and, while it can’t roll back time to ensure that only a single power format exists, it significantly closes the gap between users of UPF and the Common Power Format (CPF). In my opinion, the new standard is nothing less than the first convergent power format standard. It is also truly open.
It wasn’t an oncoming train
In terms of content, the final 2013 version of IEEE 1801 achieved everything that the authors of the February 2012 EETimes article “Power Intent Formats: Light at the End of the Tunnel?” hoped it would. One significant development since is that, rather than the Open Low-Power Methodology (OpenLPM) contribution discussed in that article, the Silicon Integration Initiative (Si2) actually contributed the entire CPF 2.0 standard to IEEE in October 2011. This was a key enabling event and it removed any legal barriers to convergence. Si2 should be saluted for making this happen. Many of the extensions and changes are explained in that article, and I will only highlight a couple here. For the final syntax and semantics of the additions and changes, please refer to the 1801-2013 standard itself.
The process towards a convergent methodology for low-power design actually started with IEEE 1801-2009 (UPF 2.0). UPF 2.0 includes commands and methods that map more easily to CPF counterparts than Accellera’s UPF 1.0. However, with the benefit of 20:20 hindsight, including UPF 1.0 in its entirety into the 1801-2009 standard froze tool support on the earlier specification, and hindered progress towards convergence. 1801-2013 put us firmly back on the path towards convergence in four main ways:
- Methodology and examples: over 100 additional pages thoroughly describe, with examples, how to use the specification for successful low-power design
- De-emphasize conflicting UPF 1.0 commands: some 12 commands and 26 options, replaced by better alternatives in 1801-2009, have been declared legacy or deprecated
- Syntactic and semantic clarifications and corrections: some 1801-2009 commands, options, and semantics have been refined or corrected
- Contributions from CPF: new capabilities introduced from Si2’s contribution, notably power models, identical in all but name to CPF’s macro models, for describing the power intent of hard IP and commands to describe low-power management cells
Figure 1 shows the new 1801-2013 power model commands and their relationship to CPF’s macro model. Note that while names have changed – this is necessary to fit in with UPF’s established terminology – there is a clear one-to-one correspondence between the two. Designers and tools alike can easily deal with different syntax given such clear one-to-one mapping.
Figure 1: Relationship between power model and macro model
There’s a difference between open source and open standards. Prior to 1801-2013, UPF was reliant on the LibertyTM format for modeling the power intent-related aspects of the specialist library cells needed to implement low-power techniques. While Liberty’s open-source license is fair and reasonable, it applies only to the current released version, which does not support everything necessary for power intent. Future extensions to Liberty are not under IEEE control. 1801-2013’s new Clause 7 “Power management cell commands,” largely unchanged from the CPF 2.0 contribution, now puts power management cell modeling under IEEE control.
Learn more at DAC
The new open, convergent standard is a major step forward to bring 1801 into the realm of advanced low-power architectures, and will enable much greater levels of interoperability with CPF. There’s still work to be done to complete the journey towards convergence – there are yet more capabilities in CPF not yet integrated into 1801 – but most low-power designers should benefit from a much improved degree of interoperability. If you want to learn more about the new standard, presenters from ARM, Broadcom, Cadence, Mentor, and Synopsys are delivering a workshop on Sunday, June 2 at Design Automation Conference in Austin entitled Low-Power Design with the New IEEE 1801-2013 Standard. If you can’t make that, there is an Accellera breakfast event on Monday, June 3 that will feature a panel session with the five presenters.
About the author:
Qi Wang joined Cadence in 1998 and is currently Technical Marketing Group Director responsible for the low-power and mixed-signal solutions. Prior to this, Qi held various R&D positions at Cadence. He’s Vice Chair of the Low Power Coalition and the Chair of the Format Working Group at Si2.org, and also represents Cadence in the IEEE 1801 Working Group.
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