Placement
Read the situation and the numbers it starts from, then pick the change you would make. Every option was run, so the answer comes from the measurement rather than from anyone's judgement, and after you choose you see what all of them did. Progress is stored in this browser.
All 2 situations in this kind, with their tables
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Which one can go at the least cost?Switch off the timing-driven pass: 735 · Switch off the routability-driven pass: 716 · Switch off both: 735
The routability pass ran in the default flow and did nothing: switching it off gives a result identical to the last micrometre, because a block using a fifth of its routing resource has no congestion for it to relieve. The timing-driven pass was doing work. Without it the block came out 3 percent larger with 2 percent more wire, and timing still closed, so on this block the pass was buying area rather than slack. Switching off both is exactly the same as switching off the timing pass alone, which says the same thing a second way.
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Which density routes cleanly on the least wire?Loosen it to a 35 percent target: 0 · Leave it at 50 percent: 0 · Pack it to a 65 percent target: 1
Packing tighter saves 5 percent of the wire, and it is the first run in which the flow reports congestion: global routing had to run extra iterations to clear it. The worst drop rises by half as well, from 0.83 percent to 1.26, with more current in less area. Loosening avoids both and pays 11 percent more wire for it, and the drop still gets worse, because the current now travels further to the straps. The default sits between two failure modes and is the only option clear of both. On the small block this knob was close to irrelevant. On a real core it moves the wire by tens of thousands of micrometres in each direction.