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BSIM3 vs BSIM4: simulation speed differences expected?

VLSIiitm

Is any difference in simulation speed expected between BSIM3 and BSIM4 model implementations in spectre? We have designs in two processes, one that uses BSIM3 and another that uses BSIM4. Large circuits in the former take longer to simulate than those in the latter. The circuits being simulated are not the same. The speed difference is a trend we have observed with many large circuits of similar sizes. In general could the pdk implementation have a significant influence on simulation speed? 

Nagendra

  • ShawnLogan

    Dear Nagendra,

    Although I have not done a direct comparison of simulation speeds using BSIM3 and BSIM4, I can provide my experiences with regard to your question:

    VLSIiitm said:
    In general could the pdk implementation have a significant influence on simulation speed? 

    Absolutely. The complexity of the PDK model has a very significant impact on simulation times. In particular, as the technology node has resulted in shorter channel lengths and now FINFET technologies, the number of parameters and effects that must be included in a model to accurately estimate performance has increased. As a result, the number of computations and size of the netlist for a given number of transistor has increased. I my experience, this has a direct impact on simulation time for a given number of transistors in a comparable netlist.

    This effect is also evident in simulation times for a given process corner using the same PDK. Some corners will consistently result in longer or shorter relative simulation times.

    I hope I understood your question correctly and provided some useful information!

    Shawn

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