Industry Expert Blogs

I am often amazed that any chips actually work. We all know that verification by simulation is based on a sampling of possible stimulus and we also know that the number of samples we provide is a tiny, tiny fraction of all of the possible stimulus patterns. Even so, verification is taking up a larger percentage of our time and increasing. We use things such as functional coverage to try and steer some of those samples towards particular areas of the design, but as system complexity grows and the amount of concurrency increases, the fraction of the total stimulus space that is actually covered is being reduced every day. Some people are also aware that most simulation never actually checks that things work correctly; they just look for obvious signs that nothing has gone wrong. As the sequential depth of designs increase, constrained random is also less likely to hit many interesting cases, so more companies are being forced to spend a greater percentage of their time directing testing. So why is it that any chips actually work?

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