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Routing layers used by Innovus early global router

Bob Ryan

When I look at the results of the Innovus place phase, the initial routing solution produced by the earlyGlobalRoute only uses 2 metal layers.  Metal 2 and 3.  Only one area where the memories have layers M1 through M4 blocked does it use M5.  I specifically defined the earlyGlobalRouteMax/Min layers  (M5/M1) but this really doesn't change anything.

Is this the normal behavior of the earlyglobalrouter?

  • Hmm. I agree that's strange. But...
    Is the design easily routable with just M2 and M3?
    It seems like if the design can be routed with lower metal layers that would be a good thing because it minimizes vias (and their associated resistance).

    At any rate, do you see the same thing with trialRoute?

    Just some things that come to mind...

  • Hi Robert.  The design is not easily routable.  The overall cell density (pre-fill) is >90% and timing is quite tight. There also some large memories that significantly block M1->M4

    I am using the foundation flow so after CTS the trialRouter uses all layers. (M1->M5).

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