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Altera_Forum's avatar
Altera_Forum
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16 years ago

Fan-out: how high is too high? (Stratix II)

We have Stratix II FPGA in one of our design. After compilation, fan-out for a global clock goes beyond 30,000, and several non-global pins have fan-out in the range of 3000 ~ 5000.

Is this too high?? Has anyone experienced problem associated with high fan-out? Could this overheat and potentially damage the chip?

Thanks,

fan

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    A global is designed to feed every register in the device, so this is perfectly fine.

    High-fanout is not a problem in the FPGA because routing lines are re-buffered all over the place. If you're not using a global for a high-fanout clock line, you can have skew issues, but timing analysis will alert you to that. As for overheating, it's not directly related to fanout, but amount of logic and toggle rates, amongst other things.

    The main point is it's absolutely fine.