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Posts Tagged ‘reuse’

Composition, Chaining, and Vertical Reuse with TrekUVM

Wednesday, August 20th, 2014

Several posts back, we introduced the idea of “composing” higher-level verification elements from low-level elements with little or no effort. We discussed how this was not possible with traditional testbench elements such as virtual sequencers and scoreboards. We showed that Breker’s graph-based scenario models can be simply combined from the block level to the cluster level, and from the cluster level to the full-chip level.

Last week, we took the unusual step of announcing a new EDA product via social media rather than a traditional press release. The news about TrekUVM clearly spread; we had a nice spike in blog readership and an even bigger spike in traffic to our Web site. Since our readers have interest in this new product, we’d like to continue talking about it and, specifically, show how it fosters model composition and vertical reuse.

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Introducing TrekUVM: Enhancing Transactional UVM Testbenches

Thursday, August 14th, 2014

In our previous four posts, we have woven a story quite different from the way we’ve talked about Breker and our technology for the past few years. Regular readers know that our focus has been on verifying system-on-chip (SoC) designs by generated multi-threaded, self-verifying C test cases to run on the SoC’s embedded processors. TrekSoC generates these test cases for simulation with RTL or ESL models; TrekSoC-Si generates test cases for emulator, FPGA prototypes, and actual silicon.

The last few posts have pointed out that TrekSoC has had to handle running in a transactional testbench since many test cases send data on or off the chip. We’ve worked hard to ensure that we can integrate easily into testbenches compliant with the Universal Verification Methodology (UVM) standard. Today we leverage this knowledge as we introduce TrekUVM, which generates multi-threaded, self-verifying test cases for a purely transactional UVM testbench.

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Transactional Design Verification with TrekSoC

Thursday, August 7th, 2014

In our last blog post, we worked our way up the conclusion that our TrekSoC product can be used to verify designs that do not contain embedded processors. As we noted, there is not a widely accepted industry term for such devices. For the moment, let’s call them “transactional designs” since the majority of them take transactions in at one end and generate transactions at the other end, sometimes for two very different protocols, and are often bidirectional in nature.

The technological argument is simple. Most SoCs also have I/O ports, both standard buses and proprietary protocols, and TrekSoC must be able to talk to them, coordinate among them, and synchronize their transactions with generated C code running in the embedded processors. A purely transactional chip and testbench form a subset of the challenge for which TrekSoC is designed, so it’s not surprising that we can help. Today’s post fills in some more details.

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Verification Reuse from Transactional Testbenches to Embedded C Code

Wednesday, July 30th, 2014

In our previous two posts, we went into considerable detail on the vertical reuse of verification information from IP block to subsystem to system. We have focused on how graph-based scenario models enable simple composition as you move up the design hierarchy. This type of reuse is not possible with traditional testbench elements such as UVM scoreboards and virtual sequencers. Once again, this is not a slam against the UVM, but rather a basic trait of constrained-random testbenches.

We skimmed over one aspect of vertical reuse: the transition from a “headless” SoC subsystem with no CPU to  full-chip simulation with our automatically generated multi-threaded C test cases running on the SoC”s embedded processors. We also skipped the question of whether or not our graph-based scenario models can generate full-chip tests for chips that do not contain processors and are not classified as SoCs. This post links these ideas together and answers the question. (more…)

A Guide to Composition for Graph-Based Scenario Models

Tuesday, July 22nd, 2014

In our last post, we went into quite a detailed discussion of how the Accellera Universal Verification Methodology (UVM) has limitations on reuse. Specifically, we showed why it is not possible to compose scoreboards and virtual sequencers together as you move up the design hierarchy from verifying blocks to verifying clusters or complete chips. In the process, information about how connected blocks communicate is lost and must be recreated in the higher-level sequencer.

We also claimed that graph-based scenario models provide more effective reuse, specifically because lower-level graphs can be composed into a higher-level graph as blocks are combined and you move up the chip hierarchy vertically. Block-level graphs compose cluster-level graphs, and cluster-level graphs compose full-chip graphs. In today’s post, we take the same example used last time and show how reuse works with graph-based scenario models rather than pure UVM testbenches.

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A Guide to Composition for Testbench Elements

Thursday, July 17th, 2014

Over the lifetime of The Breker Trekker, we’ve published numerous posts about the inherent benefits of graph-based scenario models for verification. These models allow you to pull on a rope rather than push it. They allow you to begin with the end in mind, solving backwards to determine the necessary inputs. They support advanced verification planning and debug.  They make verification modeling more pleasant. They enable both horizontal reuse over the course of a project and vertical reuse from IP block to subsystem to system.

Today we’d like to dig into a particular aspect of vertical reuse that we have not addressed in detail before. One of the goals of verification standards has been to define testbench elements that are reusable. This goal was very much in mind when the Accellera working group standardized the Universal Verification Methodology (UVM). By establishing a standard architecture, nomenclature, and application programming interface (API), UVM components are highly reusable from project to project and even company to company. However, the UVM fails at other forms of reuse.

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Would You Rather Push on a Rope or Pull It?

Tuesday, July 8th, 2014

Last week we talked once again about our familiar mantra to “begin with the end in mind” when performing SoC verification. We described the enormous value that graph-based scenario models provide by enabling automatic test case generation from desired results. TrekSoC can walk the graph backwards, from result to inputs, and generate the C code necessary to exercise true user-level test cases across multiple threads and multiple heterogenous processors.

It’s clear even to the biggest fans of the Universal Verification Methodology (UVM) that this standard breaks down at the full-chip level for an SoC containing one or more embedded processors. The UVM, for all its good points, does not encompass code executing on processors and does not provide any guidance on how to link such code with the testbench that connects the chip’s inputs and outputs. The value of scenario models for SoCs is clear. But what about large chips without embedded processors? Does Breker have a role to play there as well?

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Beginning with the End in Mind: Graphs and Formal

Monday, June 30th, 2014

I’ve written about formal analysis rather frequently in this blog, although I do not consider Breker’s products to be formal in nature. There are several reasons for this. After ten years working with formal tools, I remain personally interested in that market. I also see interesting parallels between the adoption of formal and graph-based technologies. Further, whenever we cover formal analysis we get a great response. Clearly our readers like the topic as well.

I’m returning to formal this week because of a provocative comment made by one of our customers at DAC a few weeks ago. Wolfgang Roesner from IBM participated on the show floor in a Pavilion Panel called “The Asymptote of Verification.” Among several astute observations about the attributes of graph-based scenario models, he made a comparison with formal analysis that I found especially perceptive.

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To Standardize or Not to Standardize, That Is the Question

Tuesday, May 13th, 2014

As regular readers know, Breker’s claim to fame is the automatic generation of multi-threaded, self-verifying test cases that run on multiple heterogeneous processors within an SoC. The source for the generation process is a graph-based scenario model that captures the design intent and verification space. We chose graphs as an enabling technology more than ten years ago for a number of reasons, some of which we’ll discuss in this post.

The catalyst for this discussion is a new effort within the Accellera standards body to form the Portable Stimulus Specification Proposed Working Group (PWG). Basically, Accellera has formed a proposed working group to determine whether a technical working group should be established to start developing a specification for a standard. What does this have to do with graphs, and Breker? We’ll do our best to explain the history and current status.

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Coverage from Running SoC Silicon? How Is That Possible?

Tuesday, April 1st, 2014

In our last post, we discussed some details of the demo that we showed at the DVCon and SNUG Silicon Valley events, in which TrekSoC-Si generated a test case, downloaded it into a commercial SoC (a TI OMAP4430 with dual ARM cores), and ran it in the actual chip. Our focus last time was on Breker’s unique visualization for the multi-threaded, multi-processor test cases that we generate. Specifically, we provide the same display for a test case running in silicon as we do for one running in simulation or simulation acceleration.

Even more interesting is our ability to display coverage information for test cases running in silicon. You might think that this is impossible unless we’re building coverage structures into the SoC that you fabricate. Customers have been known to build specific types of coverage metrics into their hardware, for example real-time monitoring of bus bandwidth and SoC performance. But that’s not what we’re doing; we can gather highly accurate system-level overage without changing the design a bit.

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