Coverage is My Friend

Archive for the 'Functional coverage' Category

 

Convergence Driven Coverage Modeling

“Say what??” my friend shot back when I asked him if he heard about the latest trend in coverage modeling called CDCM or Convergence Driven Coverage Modeling. I thoroughly enjoyed myself watching him scour the most obscure corners of his memory in search of something resembling my question. After all there weren’t too many coverage related topics he wasn’t aware of, let alone “the latest trend” in coverage models. Of course he had no chance to find anything as I had just made up the term to throw him off his usual cool. However, once I started explaining what I had in mind, he got really enthusiastic.

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Posted in Coverage convergence, coverage driven verification, Coverage model, efficient verification, Functional coverage, metric driven verification, verification planning

 

High Level Coverage

Unless you’ve completely isolated yourself from the wisdom of Verification and EDA pundits, you must have heard at some point that High Level Verification and High Level Synthesis are the way of the future. This has been true for at least the past 10 years and most likely is still going to be true for the next 10. The value is obviously there but there are a myriad of t’s to cross and i’s to dot until the moment some form of a high level flow will become a viable alternative to RTL verification. In the meantime we still need to find a way to make the current tried and true verification flows more efficient. So as I always do when I grapple with existential verification topics, I paid a visit to my friend Coverage and as always, he had an answer for me: High Level Coverage.

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Posted in Coverage convergence, coverage driven verification, Coverage model, efficient verification, Functional coverage, metric driven verification

 

Too Much of a Good Thing…

The few of you who regularly read this blog, may have wondered what happened to my friend Coverage in the past 3 months. It turns out he has been on a worldwide quest to collect wisdom from verification experts near and far. The other day I bumped into him and he was clearly troubled. After some prodding he grudgingly admitted to his concerns. “People are amassing coverage data as if it was an inflation hedge”, he blurted. “Soon it will overwhelm them to the point where it will be difficult to extract useful information from it and they will start ignoring it”.

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Posted in Coverage convergence, coverage driven verification, Coverage model, Coverage report, Functional coverage, Scenario coverage, Stimulus generation

 

Cloud Cover

After a surprisingly long period of sunny skies, the clouds have returned to the Bay Area. Now, although some say that predicting when a chip will be ready for tape-out is akin to forecasting the next storm, I have not decided to subtly shift the topic of this blog to the exciting world of meteorology. Instead, I wanted to explore the nexus of coverage, the kind my friend is so enthused with, and cloud computing. If you haven’t yet heard about cloud computing, you’re probably reading this blog by accident but that’s ok, my friend and I are highly socially predisposed and we’re always happy to meet new people. There are many significantly better descriptions of what cloud computing really is but I will offer my own to keep things simple. According to my irrelevant opinion, cloud computing is a combination of hardware and software resources provided as a service to some end consumer. The cloud part comes from the fact that you don’t really have to know or care about where these services reside or come from, kind of like the clouds, you don’t know where they come from, where they’ll go next, or how high up they are, only whether they provide shade, rain, that sort of thing. In any case, cloud computing is part of our new reality, so I asked my friend whether he thinks there is any potential symbiosis between the lofty clouds and our daily challenges. The answer came with lightening speed and in a thunderous voice.

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Posted in cloud computing, coverage driven verification, coverage merging, Coverage report, efficient verification, Functional coverage

 

Test the Testbench?

If you’re nostalgically inclined like me, you probably fondly remember the times when testbenches were nothing but initial blocks with assignments and forces. Alas, those days are long gone. The serenity of the static pure Verilog testbenches has been replaced by the turbulence of the dynamic SystemVerilog ones where objects come and go as they please. Granted they brought revolutionary progress to usability, re-usability, scalability, portability, flexibility but let’s not forget that we paid for all these “bilities” with a significant increase in testbench complexity. Let’s face it, verification engineers of yore had to “just” understand the design in order to do a magnificent job at verifying it whereas their modern day counterparts have to acquire significant object oriented design skills as well as ramp up on VMM, UVM, OVM, etc. before they even attempt to write a single line of verification code. Add to that the fact that design sizes grow faster than the US National Debt and that testbenches can’t afford to be left behind and you’ll see why the other day I popped this question to my friend: how do we know that the testbench works as we intended or in other words how do we test the testbench?

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Posted in coverage driven verification, Coverage model, efficient verification, Functional coverage, metric driven verification, Scenario coverage

 

The Tape-out Feast

The other day I listened in while my friend Coverage told the neighborhood kids the Thanksgiving story.  It went something like this. Once upon a time the verification engineers in the Old World design houses were not free to practice verification the way they wanted. Instead, they had to follow a strict directed test methodology imposed to them by long standing traditions. One day a group of them gathered a few of their test benches, boarded a chartered bus they called “Randflower” and left to join a new company where they could practice their own verification methodology rooted in the principles of freedom.  From then on verification engineers would be free to write coverage targets based on verification plans written in a language that everybody could understand and even testbench variables would be free to take whatever values they wanted as long as they were following some constraints. However, the road to success was not to be an easy one. They had to work long hours, come up with new methodologies and tools to take advantage of them.  The long nights and weekends of hard work soon started taking their toll. Many of them quit and moved to the software industry and those who stayed turned weak with frustration and exhaustion. But then one day a miracle happened. The indigenous designers in the company who had been working there for many years gathered together and shared their knowledge about the design with the verification engineers! This gave them the strength required to close on the remaining coverage targets and finally the fruits of their hard work were ready to be harvested. The verification engineers had a huge Tape-Out Feast where all the designers were invited to jointly celebrate the Turnkey Verification Environment they developed and thank their design counterparts for their invaluable help in their hour of need. They vowed that from then on they will write testbenches that can be easily shared among many verification groups and that they will share methodologies and best-practices for the benefit of the entire verification community.

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Posted in Coverage convergence, Coverage model, efficient verification, Functional coverage, Tape-out criteria, Uncategorized

 

The Stimulus Package

When my friend first muttered these words, I thought he decided to leave the rewarding world of verification and become a political pundit. I was dismayed because I don’t like the term pundit, it rhymes with bandit. Ever wondered why we have verification gurus and they have political pundits? In any case, it turned out it was about a far less controversial kind of stimulus package, the one you feed to your design to tickle its inputs and make its transistors go crazy. Phew!

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Posted in Coverage convergence, Coverage model, Functional coverage, Stimulus generation

 

The Butterfly Effect

You may remember the suggestive metaphor of a butterfly flapping its wings in California and causing a tornado on the other side of the globe. No, I am not attempting to apply chaos theory to coverage (although… ;-)), I am merely picking up where I left off last time and make a case that the various parts that collectively define the coverage problem are tightly connected and that the decisions we take for each part will inevitably have a profound effect on the others. Let’s take a look at some of these connections and the potential pitfalls if we ignore them.

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Posted in Coverage convergence, Coverage model, Coverage report, Functional coverage, Tape-out criteria

 

It’s All About Risk Management

Guess I should start with a disclaimer: I don’t know much about risk management. If I did, I would start an investment outfit call it “Golden Socks”.  “Golden Socks” would capitalize on the universal dream of software ownership, help fuel a software bubble and get you to buy software you cannot afford.  At the same time “Golden Socks” would bet that you won’t be able to pay maintenance for your software and have to give it back. Or something like that.

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Posted in Coverage convergence, Functional coverage, Tape-out criteria, Uncategorized

 

Coverage just a metric? No way!

Coverage and I got acquainted fairly late in my life. This has nothing to do with me getting old and my dear wife outfitting me with Abercrombie gear to cover my age, it has to do with me joining a startup called Nusym back in 2008. That’s when Coverage and I became friends. Nusym pioneered the technology that lies at the root of what the good marketing folks call “Coverage Convergence Technology”, “Intelligent Testbench” and some other tempting names that make even the most cold blooded verification engineer purr with anticipation. Nusym’s exciting technology has in the meantime become part of the Synopsys family and I have followed it partly out of loyalty to my friend Coverage.

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Posted in Coverage convergence, Coverage model, Functional coverage, Uncategorized