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Typical Overflow ?

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Hi,

I just wonder how much is the typical horizontal and vertical overflow so that the design be routable. I think this should depend on the number of metal layers in the design, I am using 6 metal layers in my design.

Thanks,

Houman



Originally posted in cdnusers.org by houmanh
Parents

  • Hi Houman,

    If you're talking about the following trialRoute output: (just before the Congestion Distribution table)

    Phase 1f route (0:00:01.4 809.2M):
    Usage: (19.5%H 20.1%V) = (6.054e+06um 7.331e+06um) = (4324061 2909069)
    OvInObst: 0 = 0/60 (0.00% H) + 0/4518 (0.00% V)
    Overflow: 74 = 4 ([b]0.00% H[/b]) + 70 ([b]0.01% V[/b])

    A very general target for trialRoute overflow numbers is 0.01%. This is not to say that the design is unroutable if the numbers are higher. You just need to investigate the congested areas and maybe try an early nanoroute to check that trialroute is correlating well. Your particular design may be fine with 0.04%, for example. If I see numbers around 0.10% or higher, there is usually a problem, but most of the time it can be fixed by adjusting the floorplan (moving rams, adding blockage around corners, etc.).

    I don't really notice this guideline changing with the number of routing layers in a design, which makes sense since it's just a percentage of overflowed gcells. If you have too many overflowed gcells in any technology, routing will be difficult.

    The Encounter User Guide has a good description of all the trialRoute results.

    I wonder if some other designers here have different numbers that work for them?

    - Kari


    Originally posted in cdnusers.org by Kari
Reply

  • Hi Houman,

    If you're talking about the following trialRoute output: (just before the Congestion Distribution table)

    Phase 1f route (0:00:01.4 809.2M):
    Usage: (19.5%H 20.1%V) = (6.054e+06um 7.331e+06um) = (4324061 2909069)
    OvInObst: 0 = 0/60 (0.00% H) + 0/4518 (0.00% V)
    Overflow: 74 = 4 ([b]0.00% H[/b]) + 70 ([b]0.01% V[/b])

    A very general target for trialRoute overflow numbers is 0.01%. This is not to say that the design is unroutable if the numbers are higher. You just need to investigate the congested areas and maybe try an early nanoroute to check that trialroute is correlating well. Your particular design may be fine with 0.04%, for example. If I see numbers around 0.10% or higher, there is usually a problem, but most of the time it can be fixed by adjusting the floorplan (moving rams, adding blockage around corners, etc.).

    I don't really notice this guideline changing with the number of routing layers in a design, which makes sense since it's just a percentage of overflowed gcells. If you have too many overflowed gcells in any technology, routing will be difficult.

    The Encounter User Guide has a good description of all the trialRoute results.

    I wonder if some other designers here have different numbers that work for them?

    - Kari


    Originally posted in cdnusers.org by Kari
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