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clkgate setup timing violation is not treated by optDesign

greenblat
Perhaps someone can help here: encounter place and route problem. when i run optDesign in setup mode and -postRoute, i get 0.6ns violation on clkgating check. optDesign doesnt fix it. it looks like during optdesign run, this violation is overlooked (because i see the WNS in the middle of the log file slightly misses the timing at -0.1ns, which i know and not related to clkgating). However in final part of the log file, when optDesign wraps things up, the big violation appears again. what can i do? is there an option to force optDesign to treat clkgating violations? i looked over setOptMode and there is only option for pre-ClockTree consideration. setting it in -postRoute mode has no effect. thanks, Ilia
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  • Tongju

    Also, it was possible that there are even larger violated paths (larger than 0.6ns) in the same design and the tool tried to put more attention to them and have to sacrifice this one (let it to have -0.6ns) for big gains in other paths. If this is the case, try "setOptMode -criticalRange 0.99" to change the way the tool to handle the small violations, you may be able to see different result.

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  • Tongju

    Also, it was possible that there are even larger violated paths (larger than 0.6ns) in the same design and the tool tried to put more attention to them and have to sacrifice this one (let it to have -0.6ns) for big gains in other paths. If this is the case, try "setOptMode -criticalRange 0.99" to change the way the tool to handle the small violations, you may be able to see different result.

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