A View from the Top: A Virtual Prototyping Blog


The Hitchhiker’s Guide to ESL – Part 2 – Abstraction and Automation

In part 2 of the Hitchhiker’s guide to system-level design we will look at development abstraction levels and required productivity improvements to keep up with the fast pace of complexity growth. In the first part of this guide we had reviewed this complexity growth from 29,000 transistors in 1979 to 2 billion 30 years later. We had likened transistors to the basic elements from which Slartibartfast designs townhomes – 104 transistors for a 4-bit register, ahem, 26 basic elements to build a town home in a 4 home complex.

BayAreaAbstractionsTo deal with the complexity increases, the abstraction level at which the design entry happens, has evolved over the last 30 years. In my first blog posts I had reviewed the evolution from transistors to gates to RTL and now to the transaction level. In Slartibartfast’s world this evolution of granularity (the level at which designers think) is equivalent to designing at a building floor plan level, house level, street level and city-level as indicated in the graph on the left.

In the good old days, Slartibartfast’s employer was an integrated design house called Texas Instrumentus, TIUS. They were doing everything from the design to the actual manufacturing of the projects to be used on various planets. TIUS at the time even had a set of design tool developed in-house, helping Slartibartfast to design the 500 houses and connections they had to do at that time in average. The automation tools were purely graphical and once a design was finished, a data file (called GDSII) was sent to manufacturing who would produce the specified worlds en mass.

Given the complexity increase from 500 houses 30 years ago to 10 billion today and a projected 500 billion in 10 years, productivity had to increase quite a bit. The oracle ITRS does not only think stuff up about the future, they also have a team of historians documenting the past. Just yesterday Slartibartfast had pulled up some of the old ITRS records to explain to his intern, that in the last 15 to 20 years alone design productivity has improved 580% through re-use and 336% through methodology improvements. And yes, in addition engineers have become “tall, thin and smarter” too 🙂

Design automation had a major role in productivity improvements. Back in 1979 Slartibartfast and his teams were drawing each house individually using schematic entry, defining the exact positions and connections manually. Design automation soon invented automated layout. Only the positions needed to be defined and then automated layout tools would automatically create the connections. Later on, at the building and street level, logic synthesis allowed to describe the intended design using a language defining all the houses, functional units and their individual connections. The logic synthesis tools would then suggest an implementation of the desired functionality based on speed, area and power consumption constraints set by the user.

In addition, re-use played a crucial role. Instead of designing each portion of the bay area by hand, the basic building blocks were pulled from pre-defined libraries. At first, for “small block re-use”, libraries of basic design elements were introduced in about 1997: kitchens, bathrooms, hallways, gardens, doors etc. Later, for large block re-use starting about 1999, complete houses, town homes, theatres, schools, streets and intersections increased productivity even further. Very large block reuse really just found its adoption  a couple of years ago around 2007. Now re-use happened at a much larger scale. For specific interfaces, like for example the interface to the sea called USH (Universal Serial Harbor), it really did not make sense to design it from scratch every time. There were Intellectual Property (IP) providers, who could provide design teams with pre-defined USH designs ready to be included. They typically had even tested them using various manufacturing technologies so that Slartibartfast and his teams did not have to worry about it. The Oakland harbor is a good example, Slartibartfast fondly still remembers the negotiation with SYNOPYSOS, the biggest supplier of connectivity IP, from which he had bought the Oakland USH interface and it immediately worked perfectly.

Design for sure has changed over the last 30 years and at times if had been difficult for Slartibartfast to keep up with all the new tools and methodologies. The next installment of this series will deal with simulation and verification. Not only does the bay area need to be implemented fast and on time, but it also has to be verified and validated. That means it has to do what the specification requests and it also needs to meet the customer’s intent. In order for this to happen, we will discuss technologies for simulation and verification in the next blog post.

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