Timing driven compilation - appears to not balance setup-hold window

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When multi corner compile is on, the slacks are adjusted according to all timing models - slow fast, high, low temperature. So looking at only the result for one models timing, this may not appear optimized because other models may have contradicting requirements. In multi corner mode, a global compromise is taken.

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as far as I am aware the timing tool does not target balanced slack. It targets a timing pass for all corners. You can try slow clock and see.

TQ however advises on balanced slack at io since corners are less predictable.