It seems to be the season of verification. The Universal Verification Methodology (UVM 1.2) is being discussed across conferences. Dennis Brophy, director of Strategic Business Development, Mentor Graphics, says that UVM 1.2 release is imminent, and UVM remains a topic of great interest.
Biggest verification mistakes
Before I add Dennis Brophy’s take on UVM 1.2, I discussed with Dr. Wally Rhines, chairman and CEO, Mentor Graphics Corp. the intricacies regarding verification. First, I asked him regarding the biggest verification mistakes today.
Dr. Rhines said: “The biggest verification mistake made today is poor or incomplete verification planning. This generally results in underestimating the scope of the required verification effort. Furthermore, without proper verification planning, some teams fail to identify which verification technologies and tools are appropriate for their specific design problem.”
Would you agree that many companies STILL do not know how to verify a chip?
Dr. Rhines added: “I would agree that many companies could improve their verification process. But let’s first look at the data. Today, we are seeing that about 1/3 of the industry is able to achieve first silicon success. But what is interesting is that silicon success within our industry has remained constant over the past ten years (that is, the percentage hasn’t become any worse).
“It appears that, while design complexity has increased substantially during this period, the industry is at least keeping up with this added complexity through the adoption of advanced functional verification techniques.
“Many excellent companies view verification strategically (and as an advantage over their competition). These companies have invested in maturing both their verification processes and teams and are quite productive and effective. On the other hand, some companies are struggling to figure out the entire SoC space and its growing complexity and verification challenges.”
How are companies trying to address those?
According to him, the recent Wilson Research Group Functional Verification Study revealed that the industry is maturing its verification processes through the adoption of various advanced functional verification techniques (such as assertion-based verification, constrained-random simulation, coverage-driven techniques, and formal verification). Complexity is generally forcing these companies to take a hard look at their existing processes and improve them.
Getting business advantage
Are companies realizing this and building an infrastructure that gets you business advantage?
He added that in general, there are many excellent companies out there that view verification strategically and as an advantage over their competition, and they have invested in maturing both their verification processes and teams. On the other hand, some other companies are struggling to figure out the entire SoC space and its growing complexity and verification challenges.
When should good verification start?
When should good verification start — after design; as you are designing and architecting your design environment?
Dr. Rhines noted: “Just like the design team is often involved in discussion during the architecture and micro-architecture planning phase, the verification team should be an integral part of this process. The verification team can help identify architectural aspects of the design that are going to be difficult to verify, which ultimately can impact architectural decisions.”
Are folks mistaken by looking at tools and not at the verification process itself? What can be done to reverse this?
He said: “Tools are important! However, to get the most out of the tools and ensure that the verification solution is an efficient and repeatable process is important. At Mentor Graphics, we recognize the importance of both. That is why we created the Verification Academy, which focuses on developing skills and maturing an organization’s functional verification processes.”
What all needs to get into verification planning as the ‘right’ verification path is fraught with complexities?
Dr. Rhines said: “During verification planning, too many organizations focus first on the “how” aspect of verification versus the “what.” How a team plans to verify its designs is certainly important, but first you must identify exactly what needs to be verified. Otherwise, something is likely to slip through.
“In addition, once you have clearly identified what needs to be verified, it’s an easy task to map the functional verification solutions that will be required to productively accomplish your verification goals. This also identifies what skill sets will need to be developed or acquired to effectively take advantage of the verification solutions that you have identified as necessary for your specific problem.”
How is Mentor addressing this situation?
Mentor Graphics’ Verification Academy was created to help organizations mature their functional verification processes—and verification planning is one of the many excellent courses we offer.
In addition, Mentor Graphics’ Consulting provides customized solutions to technical challenges on real projects with real schedules. By helping customers successfully integrate advanced functional verification technologies and methodologies into their work flows, we help ensure they meet their design and business objectives.
Five recommendations for verification
Finally, I asked him, what would be your top five recommendations for verification?
Here are the five recommendations for verification from Dr. Rhines:
* Ensure your organization has implemented an effective verification planning process.
* Understand which verification solutions and technologies are appropriate (and not appropriate) for various classes of designs.
* Develop or acquire the appropriate skills within your organization to take advantage of the verification solutions that are required for your class of design.
* For the SoC class of designs, don’t underestimate the effort required to verify the hardware/software interactions, and ensure you have the appropriate resources to do so.
* For any verification processes you have adopted, make sure you have appropriate metrics in place to help you identify the effectiveness of your process—and identify opportunities for process improvements in terms of efficiency and productivity.
Its a pleasure to talk to Dr. Walden (Wally) C. Rhines, chairman and CEO, Mentor Graphics Corp. On his way to DAC 2013, where he will be giving a ten-minute “Visionary Talk”, he found time to speak with me. First, I asked him given that the global semiconductor industry is entering the sub-20nm era, will it continue to be ‘business as usual’ or ‘it’s going to be different this time’?
Dr. Rhines said: “Every generation has some differences, even though it usually seems like we’ve seen all this before. The primary change that comes with “sub-20nm” is the change in transistor structure to FinFET. This will give designers a boost toward achieving lower power. However, compared to 28nm, there will be a wafer cost penalty to pay for the additional process complexity that also includes two additional levels of resolution enhancement.”
Impact of new transistor structures
How will the new transistor structures impact on design and manufacturing?
According to him, the relatively easy impact on design is related to the simulation of a new device structure; models have already been developed and characterized but will be continuously updated until the processes are stable. More complex are the requirements for place and route and verification; support for “fin grids” and new routing and placement rules has already been implemented by the leading place and route suppliers.
He added: “Most complex is test; FinFET will require transistor-level (or “cell-aware”) design for test to detect failures, rather than just the traditional gate-level stuck-at fault models. Initial results suggest that failure to move to cell-aware ATPG will result in 500 to 1000 DPM parts being shipped to customers.
“Fortunately, “cell-aware” ATPG design tools have been available for about a year and are easily implemented with no additional EDA cost. Finally, there will be manufacturing challenges but, like all manufacturing challenges, they will be attacked, analyzed and resolved as we ramp up more volume.”
Introducing 450mm wafer handling and new lithography
Is it possible to introduce 450mm wafer handling and new lithography successfully at this point in time?
“Yes, of course,” Dr. Rhines said. “However, there are a limited number of companies that have the volume of demand to justify the investment. The wafer diameter transition decision is always a difficult one for the semiconductor manufacturing equipment companies because it is so costly and it requires a minimum volume of machines for a payback. In this case, it will happen. The base of semiconductor manufacturing equipment companies is becoming very concentrated and most of the large ones need the 450mm capability.”
What will be the impact of transistor variability and other physics issues?
As per Dr. Rhines, the impact should be significant. FinFET, for example requires controlling physical characteristics of multiple fins within a narrow range of variability. As geometries shrink, small variations become big percentages. New design challenges are always interesting for engineers but the problems will be overcome relatively quickly.
Agnisys Inc. was established in 2007 in Massachusetts, USA, with a mission to deliver innovative automation to the semiconductor industry. The company offers affordable VLSI design and verification tools for SoCs, FPGAs and IPs that makes the design verification process extremely efficient.
Agnisys’ IDesignSpec is an award winning engineering tool that allows an IP, chip or system designer to create the register map specification once and automatically generate all possible views from it. Various outputs are possible, such as UVM, OVM, RALF, SystemRDL, IP-XACT etc. User defined outputs can be created using Tcl or XSLT scripts. IDesignSpec’s patented technology improves engineer’s productivity and design quality.
The IDesignSpec automates the creation of registers and sequences guaranteeing higher quality and consistent results across hardware and software teams. As your ASIC or FPGA design specification changes, IDesignSpec automatically adjusts your design and verification code, keeping the critical integration milestones of your design engineering projects synchronized.
Register verification and sequences consume up to 40 percent of project time or more when errors are the source of re-spins of SoC silicon or an increase in the number of FPGA builds. IDesignSpec family of products is available in various flavors such as IDSWord, IDSExcel, IDSOO and IDSBatch.
IDesignSpec more than a tool for creating register models!
Anupam Bakshi, founder, CEO and chairman, Agnisys, said: “IDesignSpec is more than a tool for creating register models. It is now a complete Executable Design Specification tool. The underlying theme is always to capture the specification in an executable form and generate as much code in the output as possible.”
The latest additions in the IDesignSpec are Constraints, Coverage, Interrupts, Sequences, Assertions, Multiple Bus Domains, Special Registers and Parameterization of outputs.
“IDesignSpec offers a simple and intuitive way to specify constraints. These constraints, specified by the user, are used to capture the design intent. This design intent is transformed into code for design, verification and software. Functional Coverage models can be automatically generated from the spec so that once again the intent is captured and converted into appropriate coverage models,” added Bakshi.
Using an add-on function of capturing Sequences, the user is now able to capture various programming sequences in the spec, which are translated into C++ and UVM sequences, respectively. Further, the interrupt registers can now be identified by the user and appropriate RTL can be generated from the spec. Both edge sensitive and level interrupts can be handled and interrupts from various blocks can be stacked.
Assertions can be automatically generated from the high level constraint specification. These assertions can be created with the RTL or in the external files such that they can be optionally bound to the RTL. Unit level assertions are good for SoC level verification and debug, and help the user in identifying issues deep down in the simulation hierarchy.
The user can now identify one or more bus domains associated with Registers and Blocks, and generate appropriate code from it. Special Registers such as shadow registers and register aliasing is also automatically generated.
Finally all of the outputs such as RTL, UVM, etc., can be parameterized now, so that a single master specification can be used to create outputs that can be parameterized at the elaboration time.
How is IDesignSpec working as chip-level assertion-based verification?
Bakshi said: “It really isn’t an assertion tool! The only assertion that we automatically generate is from the constraints that the user specifies. The user does not need to specify the assertions. We transform the constraints into assertions.”
It is always a pleasure speaking with Dr. Walden (Wally) C. Rhines, chairman and CEO, Mentor Graphics Corp. I met him on the sidelines of the 13th Global Electronics Summit, held at the Chaminade Resort & Spa, Santa Cruz, USA.
Status of global EDA industry
First, I asked Dr. Rhines how the EDA industry was doing. Dr. Rhines said: “The global EDA industry has been doing pretty well. The results have been pretty good for 2012. In general, the EDA industry tends to follow the semiconductor R&D by at least 18 months.”
For the record, the electronic design automation (EDA) industry revenue increased 4.6 percent for Q4 2012 to $1,779.1 million, compared to $1,700.1 million in Q4 2011.
Every region, barring Japan, grew in 2012. The Asia Pacific rim grew the fastest – about 12.5 percent. The Americas was the second fastest region in terms of growth at 7.4 percent, and Europe grew at 6.8 percent. However, Japan decreased by 3 percent in 2012.
In 2012, the segments that have grown the fastest within the EDA industry include PCB design and IP, respectively. The front-end CAE (computer aided engineering) group grew faster than the backend CAE. By product category, CAE grew 9.8 percent. The overall growth for license and maintenance was 7 percent. Among the CAE areas, design entry grew 36 percent and emulation 24 percent, respectively.
DFM also grew 28 percent last year. Overall, PCB grew 7.6 percent, while PCB analysis was 25 percent. IP grew 12.6 percent, while the verification IP grew 60 percent. Formal verification and power analysis grew 16 percent each, respectively. “That’s actually a little faster than how semiconductor R&D is growing,” added Dr. Rhines.
Status of global semicon industry
On the fortunes of the global semiconductor industry. Dr. Rhines said: “The global semiconductor industry grew very slowly in 2012. Year 2013 should be better. Revenue was actually consolidated by a lot of consolidations in the wireless industry.”
According to him, smartphones should see further growth. “There are big investments in capacities in the 28nm segment. Folks will likely redesign their products over the next few years,” he said. “A lot of firms are waiting for FinFET to go to 20nm. People who need it for power reduction should benefit.”
“A lot of people are concerned about Japan. We believe that Japan can recover due to the Yen,” he added.
It is always a pleasure to chat with Dr. Wally (Walden C.) Rhines, chairman and CEO, of Mentor Graphics. I chatted with him, trying to understand gigascale design, verification trends, strategy for power-aware verification, SERDES design challenges, migrating to 3D FinFET transistors, and Moore’s Law getting to be “Moore Stress”!
Chip design in gigascale, hertz, complex
First, I asked him to elaborate on how implementation of chip design will evolve, with respect to gigascale design, gigahertz and gigacomplex geometries.
He said: “Thanks to close co-operation among members of the foundry ecosystem, as well as cooperation between IDMs and their suppliers, serious development of design methods and software tools is running two to three generations ahead of volume manufacturing capability. For most applications, “Gigascale” power dissipation is a bigger challenge than managing the complexity but “system-level” power optimization tools will continue to allow rapid progress. Thermal analysis is becoming part of the designer’s toolkit.”
Functional verification is continually challenged by complexity but there have been, and continue to be, many orders of magnitude improvement in performance just from adoption of emulation, intelligent test benches and formal methods so this will not be a major limitation.
The complexity of new physical design problems will, however, be very challenging. Design problems ranging from basic ESD analysis, made more complex due to multiple power domains, to EMI, electromigration and intra-die variability are now being addressed with new design approaches. Fortunately, programmable electrical rule checking is being widely adopted and will help to minimize the impact of these physical effects.
Is verification keeping up?
How is the innovation in verification keeping up with trends?
Dr. Rhines added that over the past decade, microprocessor clock speeds have leveled out at 3 to 4 GHz and server performance improvement has come mostly from multi-core architectures. Although some innovative approaches have allowed simulators to gain some advantage from multi-core architectures, the speed of simulators hasn’t kept up with the growing complexity of leading edge chips.
Emulators have more than made up the difference. Emulators offer more than four orders of magnitude faster performance than simulators and emulators do so at about 0.005X the cost per cycle of simulation. The cost of power per year is more than one third the cost of hardware in a large simulation farm today, while emulation offers a 12X savings in power per verification clock cycle. For those who design really complex chips, a combination of emulation and simulation, along with formal methods and intelligent test benches, has become standard.
At the block and subsystem level, high level synthesis is enabling the next move up in design and verification abstraction. Since verification complexity grows at about the square of component count, we have plenty of room to handle larger chips by taking advantage of the four orders of magnitude improvement through emulation plus another three or four orders of magnitude through formal verification techniques, two to three orders of magnitude from intelligent test benches and three orders of magnitude from higher levels of abstraction.
By applying multiple engines and multiple abstraction levels to the challenge of verifying chips, the pressure is on to integrate the flow. Easily transitioning and reusing verification efforts from every level—including tests and coverage models, from high level models to RTL and from simulation to emulation—is being enabled through more powerful and adaptable verification IP and high level, graph-based test specification capabilities. These are keys to driving verification reuse to match the level of design reuse.
Powerful verification management solutions enable the collection of coverage information from all engines and abstraction levels, tracking progress against functional specifications and verification plans. Combining verification cycle productivity growth from emulation, formal, simulation and intelligent testing with higher verification abstraction, re-use and process management provides a path forward to economically verifying even the largest, most complex chips on time and within budget.
Good power-aware verification strategy for SoCs
What should be a good power-aware verification strategy for SoCs
According to him, the most important guideline is to start power-aware design at the highest possible level of system description. The opportunity to reduce system power is typically an order of magnitude greater at the system level than at the RTL level. For most chips today, that means at least the transaction level when the design is still described in C++ or SystemC.
Significant experience and effort should then be invested at the RTL level using synthesis and UPF-enabled simulation. Verification solutions typically automate the generation of correctness checks for power-control sequences and power-state coverage metrics. As SoC power is typically managed by software, the value of a hardware/software co-verification and co-debug solution in simulation and emulation becomes apparent in power-management verification at this level.
As designers proceed to the gate and transistor level, accuracy of power estimation improves. That is why gate level analysis and verification of the fully implemented power management architecture is important. Finally, at the physical layout, designers traditionally were stuck with whatever power budget was passed down to them. Now,they increasingly have power goals that can be achieved using dozens of physical design techniques that are built into the place and route tools.
Today, EDA requires specialization. Elaborating on EDA over the past decade, Dr. Walden (Wally) C. Rhines, chairman and CEO, of Mentor Graphics, and vice chairman of the EDA Consortium, USA, said that PCB design has been flat despite growth in analysis, DFM and new emerging markets. Front end design has seen growth from RF/analog design and simulation, and analysis As design methodologies mature, EDA expenditures stop growing. He was speaking at Mentor Graphics’ U2U (User2User) conference in Bangalore, India.
Most of the EDA revenue growth comes from major new design methodologies, such as ESL, DFM, analog-mixed signal and RF. PCB design trend continues to be flat, and includes license and maintenance. The IC layout verification market is pointing to a 2.1 percent CAGR at the end of 2011. The RTL simulation market has been growing at 1.3 percent CAGR for the last decade. The IC physical implementation market has been growing at 3,4 percent CAGR for the last decade.
Growth areas in EDA from 2000-2011 include DFM at 28 percent CAGR, formal verification at 12 percent, ESL at 11 pecent, and IC/ASIC analysis at 9 percent, respectively.
What will generate the next wave of electronic product design challenges, and the future growth of EDA? This would involve solving new problems that are not part of the traditional EDA, and ‘do what others don’t do!
Methodology changes that may change EDA
There are five factors that can make this happen. These are:
* Low power design beyond RTL (and even ESL).
* Functional verification beyond simulation.
* Physical verification beyond design for manufacturability.
* Design for test beyond compression.
* System design beyond PCBs
Low power design at higher levels
Power affects every design stage. Sometimes, designing for low power at system level is required. System level optimization has the biggest impact on power/performance. And, embedded software is a major point of leverage.
Embedded software has an increasing share of the design effort. Here, Mentor’s Nucleus power management framework is key. It has an unique API for power management, enables software engineers to optimize power consumption, and reduces lines of application code. Also, power aware design optimizes code efficiency.
Functional verification beyond RTL simulation
The Verification methodology standards war is over. UVM is expected to grow by 286 percent in the next 12 months. Mentor Graphics Questa inFact is the industry’s most advanced testbench automation solution. It enables Testbench re-use and accelerates time-to-coverage. Intelligent test bench facilitates linear transition to multi-processing.
Questa accelerates the hardware/software verification environment. In-circuit emulation has been evolving to virtual hardware acceleration and embedded software development. Offline debug increases development productivity. A four-hour on-emulator software debug session drops to 30 minutes batch run. The offline debug allows 150 software designers to jumpstart debug process on source code. Virtual stimulus increases the flexibility of the emulator. As an example, Veloce is 700x more efficient than large simulation farms.
Physical verification beyond design for manufacturability
The Calibre PERC is a new approach to circuit verification. The Calibre 3DSTACK is the verification flow for 3D.