Wires and routing
Each summary describes a real run. Say whether the metric lands over or under the number asked, and the measured value is revealed against it. Keys o and u answer, h shows a hint, and Enter moves on. Guessing gets half right, so the score only means something above that. Progress is stored in this browser.
All 10 summaries in this family, with their numbers
-
gcd on Nangate45, 45 nanometre: Is the total routed wire length over 5000 micrometres?3605 micrometres, so under
3605 micrometres for 648 nets is an average of about 5.6 micrometres a net, which is the right order for a block this small: most nets connect neighbours. Wire length scales with the square root of the area for a given cell count, so it is one of the easier numbers to estimate once you know the die.
-
gcd on Nangate45, 45 nanometre: Is the total routed wire length over 5000 micrometres?6099 micrometres, so over
The same netlist routes 3605 micrometres at the default utilization and 6099 here. Spreading a design out lengthens every net, which costs delay and power and forces repair to add buffers. Empty space is not free.
-
gcd on Nangate45, 45 nanometre: Is the total routed wire length over 4500 micrometres?3908 micrometres, so under
Taking away seven layers added only 8 percent of wire, and the design still routed with no violations. On a small block the router has room to detour; the same restriction on a dense design is what makes routing fail. Knowing which designs are sensitive is the useful part.
-
aes on Nangate45, 45 nanometre: Is the total routed wire length over 100000 micrometres?274995 micrometres, so over
275000 micrometres is 76 times the gcd figure for 28 times the cells, because a larger block has longer average nets as well as more of them. This superlinear growth is the reason wire delay dominates at scale and why hierarchy exists.
-
gcd on Nangate45, 45 nanometre: Did the thinner power grid change the signal wire length by more than 5 percent?0.2 percent, so under
3599 micrometres against 3605, a fifth of a percent. At this density the grid was never what the signals were routing around. On a dense block with a heavy grid the two do compete, which is the trade a power plan makes: enough metal to hold the voltage, not so much that the signals cannot get through.
-
aes on Nangate45, 45 nanometre: Did the detailed router ever see more than 1000 violations at once?5434 violations, in its first pass, so over
5434 after the first pass, then 2304, 1925, 100, and zero. A large count early is normal and says nothing on its own; what matters is whether each pass clears most of what the last one left. A count that stops falling is the one to worry about.
-
ibex on Nangate45, 45 nanometre: Does this core route more than 200000 micrometres of wire?262811 micrometres, so over
262811 micrometres against 275000 for aes, within five percent, for two designs that do entirely different things. Wire length follows the cell count and the floorplan far more than it follows what the logic computes, which is what makes it estimable at all.
-
jpeg, an image encoder on Nangate45, 45 nanometre: Does it route more than 500000 micrometres of wire?568656 micrometres, so over
568656 micrometres, 2.2 times the ibex figure for 3.8 times the cells. Wire length per cell actually falls here, because this design is packed at 85 percent utilization against 51 and its logic is more local. Density buys short wires, and pays for them in congestion and in voltage drop.
-
gcd, run three times on Nangate45, 45 nanometre: Is the spread in wire length across these three over 30 percent?22 percent, largest against smallest, so under
4193, 3605 and 3448 micrometres: 22 percent from end to end, and monotonic, so packing tighter does shorten wires. The effect is real but mild compared with the extreme case, where dropping to 9 percent utilization added 69 percent. Most of the damage lives outside the range anyone would actually choose.
-
aes, run twice on Nangate45, 45 nanometre: Did the four-layer run route more than 260000 micrometres?274995 micrometres, so over
274995 against 222438, 24 percent more wire for the same design, where the gcd block paid only 8 percent. A bigger design has more long nets, and long nets are the ones that need the upper layers, so the cost of a thin stack grows with the block. Both runs still closed, which says more about how much slack this design had than about the restriction.