same constraint, different compiling time

Hello David,

may be the question sounds heretical. Could it be, that you're spending at lot of effort constraining a clock that is simply unrelated? If it's unrelated, the only condition to be met is, that the counter driven by this clock must be fast enough to follow the input. Synchronization to system clock must be performed anyway, but doesn't require constraints.

If you want to simply tell a common fmax for all clock inputs, the first syntax should be appropriate, unless you don't combine clock inputs in your logic, which probably isn't the case.

Regards,

Frank