What is CRPR in PrimeTime timing reports?

We used the example below to explain how derate / OCV works in PrimeTime. An interesting corner case is that, in both setup time and hold time analysis, cell u0 is subject to different derating. Obviously, this introduces unnecessary pessimism in timing analysis. PrimeTime introduces a concept called Clock Reconvergence Pessimism Removal, or CRPR, to address this issue.

Timing Slack with Derate

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How to calculate timing slack using OCV

In previous post, we talked about the concepts of OCV, AOCV and POCV. In this post, we will use an example to further illustrate how to calculate timing slack using OCV.

An Example

Let’s assume OCV will derate 10% for clock cells, and 20% for data path. An reg-to-reg path along with delay values is shown in the diagram below.

Timing Slack with Derate

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What are OCV / AOCV / POCV?

In manufacture, chips on the same die may suffer from variations due to process, voltage or temperature change, thus transistors can be faster or slower in different dies. To compensate the variation, STA introduces a concept called On Chip Variation, or OCV. During design time, extra timing margins are added in timing analysis.

OCV has been evolved to Advanced OCV / AOCV, or even Parametric OCV / POCV. In this post, we will cover these three concepts.

Continue reading → What are OCV / AOCV / POCV?