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Altera_Forum's avatar
Altera_Forum
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11 years ago

Design fits on Cyclone IV but not Cyclone V

I have a device that fits on a EP4CE22F17C6 but not on a 5CEFA2F23C8N. From my understanding, there are more logic elements (25K vs 22K) and memory on the Cyclone V device. The design barely fits, and after synthesis LE expected usage is ~10% higher than what either device can support. With the Cyclone IV, Quartus goes on and attempts fitting, fails at first, reattempts and finally barely fits the design. With the Cyclone V, Quartus doesn't even attempt fitting. How can I make the fitter at least attempt?

3 Replies

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

    I am not sure but maybe the fitter Option to start more than one attempt is not activated automatically in Cyclone V Projects. I'd suggest to check this Option in Assignments -> Settings -> Fitter settings

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

    I see the option "Limit to One Fitting Attempt Off" when compiling for Cyclone IV. I do not see this option when compiling for Cyclone V. Has it been removed? How can I emulate its behavior with Cyclone V?

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

    I believe the extra fitting attempts have been deprecated, if not disabled. On subsequent fitting attempts, the fitter tries less and less to meet timing, and spends tons of time focusing on routability. Most of the time this occurs it spends a lot of time and still no-fits, and the few times it does fit the results are so bad they're usually useless.

    I would recommend:

    - Assignments -> Settings -> Fitter ->

    Placement Effort = 8

    Router Effort Level = Maximum

    Optimize Timing = Off(This is the killer for performance)

    You might also want to try turning Optimize Hold Timing off, although that's not part of the normal extra fit passes. This would make a design that might not functionally work, but would get a fit(which is what the extra fit passes often do).