Human psychology points to the fact that constant repetition of any statement registers the same into sub-conscious mind and we start believing into it. The statement, “Verification claims 70% of the schedule” has been floating around in articles, keynotes and discussions for almost 2 decades so much that even in absence of any data validating it, we believed it as a fact for a long time now. However, the progress in verification domain indicate that this number might actually by a "FACT".
20 years back, the designs were few K gates and the design team verified the RTL themselves. The test benches and tests were all developed in HDLs and sophisticated verification environment was not even part of the discussions. It was assumed that the verification accounted for roughly 50% of the effort.
Since then, the design complexity has grown exponentially and state of the art test benches with lot of metrics have pre empted legacy verification. Instead of designers, a team of verification engineers is deployed on each project to overcome the cumbersome task. Verification still continues to be an endless task demanding aggressive adoption of new techniques quite frequently.
A quick glance at the task list of verification team shows following items –
- Development of metric driven verification plan based on the specifications.
- Development of HVL+Methodology based constrained random test benches.
- Development of directed test benches for verifying processor integration in SoC.
- Power aware simulations.
- Analog mixed signal simulations.
- Debugging failures and regressing the design.
- Add tests to meet coverage goals (code, functional & assertions).
- Formal verification.
- Emulation/Hardware acceleration to speed up the turnaround time.
- Performance testing and usecases.
- Gate level simulations with different corners.
- Test vector development for post silicon validation.
The above list doesn’t include modeling for virtual platforms as it is still in early adopter stage. Along with the verification team, significant quanta of cycles are added by the design team towards debugging. If we try to quantify the CPU cycles required for verification on any project, the figures would easily over shadow any other task of the ASIC design cycle.
Excerpts from the Wilson Research study (commissioned by Mentor) indicate interesting data (approximated) –
- The industry adoption of code coverage has increased to 72 percent by 2010.
- The industry adoption of assertions had increased to 72 percent by 2010.
- Functional coverage adoption grew from 40% to 72% from 2007 to 2010.
- Constrained-random simulation techniques grew from 41% in 2007 to 69% in 2010.
- The industry adoption of formal property checking has increased by 53% from 2007 to 2010.
- Adoption of HW assisted acceleration/emulation increased by 75% from 2007 to 2010.
- Mean time a designer spends in verification has increased from an average of 46% in 2007 to 50% in 2010.
- Average verification team size grew by a whopping 58% during this period.
- 52% of chip failures were still due to functional problems.
- 66% of projects conitnue to be behind schedule. 45% of chips require two silicon passes and 25% require more than two passes.
While the biggies of the EDA industry are evolving the tools incessantly, a brigade of startups has surfaced with each trying to check this exorbitant problem of verification. The solutions are attacking the problem from multiple perspectives. Some of them are trying to shorten the regressions cycle, some moving the task from engineers to tools, some providing data mining while others providing guidance to reduce the overall efforts.
The semiconductor industry is continuously defining ways to control the volume of verification not only by adding new tools or techniques but redefining the ecosystem and collaborating at various levels. The steep rise in the usage of IPs (e.g. ARM’s market valuation reaching $12 billion, and Semico reporting the third-party IP market grew by close to 22 percent) and VIPs (read posts 1, 2, 3) is a clear indicative of this fact.
So much has been added to the arsenal of verification teams and their ownership in the ASIC design cycle that one can safely assume the verification efforts having moved from 50% in early 90s to 70% now. And since the process is still ON, it would be interesting to see if this magic figure of 70% still persist or moves up further!!!