At DAC two years ago Cadence launched it’s Common Power Format (CPF), while down the hall Mentor, Synopsys, Magma and several semiconductor firms launched the rival Uniform Power Format (UPF). Cadence wanted to keep control of its power specification format, to which its competitors took huge exception. For a long time it looked as if ne’er the twain would meet. Having two rival power specs is a real disservice to the design community.
The dissidents submitted UPF to IEEE’s specification process, which recently yielded IEEE1801-2009, based on UPF 2.0. Cadence submitted CPF to the smaller Si2 consortium, which released v. 1.0 in March, 2007 and v. 1.1 in September, 2008. Si2’s Low-Power Coalition set out last year to try to merge the two power specs.
This afternoon Cadence’s Qi Wang, vice-chair of the Low-Power Coalition Technical Steering Group, addressed the Low-Power Coalition Workshop: Advances in Low-Power Design Throughout the Design Flow. According to Wang, “Interoperability between CPF and UPF to support multi-vendor tools flow is a major focus for Si2’s Low-Power Coalition in 2009.”
Power format interoperability objectives include:
- Identify interoperable subset of commands and options;
- Publish it as a starting point for companies to adhere;
- Provide guidance for commands outside of the interoperable subset;
- Make recommendations for future CPF/UPF extensions.
Wang highlighted both the similarities and differences between CPF 1.1 and IEEE 1001-2009. Regarding similarities, Wang detailed some ways in which UPF has evolved to be more like CPF, including the “supply sets” concept, which is like CPF’s “power domains” concept. CPF 1.1 also has new features that make it more like UPF. Wang explained it was important for the standard to converge, because we “need better interoperability within a mixed-format and mixed-tools low-power design flow.”
The remaining differences are non-trivial. CPF 1.1 provides macro model support for complex IP, and it uses constraints to drive MMMC timing optimization and analysis. UPF has more options to specify isolation and level shifter rules. It also has additional simulation semantics for different power states.
The Low-Power Coalition proposes some interoperable power format guidelines:
- EDA tools must follow the standards strictly
- Companies should adhere to identified interoperability subsets, which it is working to define.
The group plans to send a request to the IEEE1801 committee asking that it migrate UPF to support physically disjoint power domains and equivalent control pins. With the planned release of CPF 1.2 next year, CPF will move much closer to UPF. If the latter continues on a similar path toward convergence, designer engineers will have a much easier time of it going forward.