Voltage drop
Read the map, then answer. Some questions give you four readings to choose between, some show two maps and ask which is healthy, and some ask you to click the region itself. Keys 1 to 4 choose an option, a and b choose a map, and Enter moves on. Every answer is followed by a description of what the map shows and the numbers behind it. Progress is stored in this browser.
All 5 maps in this family, described
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Which grid is the healthier one?the same design, two power grids, voltage drop across the core
Two maps of similar shape: a cool band at the top, a dark red region through the middle, and warmer colours below. Their colour legends read up to 3.698 millivolts on the left and 13.921 on the right.
They look alike because each map normalizes its colours to its own range, so the worst region is always dark red whatever the numbers are. The legends differ by nearly four times: 3.7 millivolts against 13.9. Read the scale before reacting to the colour, on this map and on every other one a tool draws.
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Click the region where the supply has sagged the most.gcd on Nangate45 with narrowed, widely spaced power straps
A gradient from a cool band along the top to a dark red region filling the right and centre of the middle, with orange along the bottom.
The drop grows with distance from where the current enters, so the worst place is the area furthest from the straps that feed it, not the area with the most cells. Fixing it means getting metal closer to that region: more straps, wider ones, or a connection from another direction.
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Which of these supplies is in better shape?two designs on two processes, voltage drop across the core
Both show deep red bands through the middle on a cooler background. The left legend runs to 845 microvolts, the right to 13.921 millivolts.
The left one is sixteen times healthier and looks every bit as alarming, because each map stretches its colours across its own range. On its 1.8 volt supply, 845 microvolts is five hundredths of a percent, while the right is 1.14 percent of 1.1 volts. Two maps of different designs on different processes cannot be compared by colour at all: only the numbers beside them mean anything.
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These two share a process and a supply. Which one is worse?two designs on Nangate45, both on the same 1.1 volt supply, drop on the ground net
Both are banded, cool at the edges and deep red in a broad stripe across the middle. The left legend runs to 8.866 millivolts, the right to 14.419 millivolts.
This is the case the other voltage pair does not cover. When the process and the supply match, the legends are in the same units against the same 1.1 volts, so the numbers compare directly: 0.81 percent on the left against 1.31 percent on the right. The colours still do not compare, because each map stretches its palette over its own range, and the two deepest reds here stand for readings that differ by a factor of 1.6. So the rule survives intact. Read the legend, then decide. One more thing worth knowing about these maps: they are drawn on the ground net, so what they show is the ground rising under the cells rather than the supply sagging above them. The same runs report 0.83 and 1.54 percent on the supply, and a cell that sits in both hot spots loses from both ends.
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What are the thick stripes crossing the whole die?ibex on Nangate45, every wire on the block including the supply nets
Dense signal routing in green, yellow and red, crossed by thick pink stripes that run the full width of the die at a regular spacing. A dark blue region at the bottom right has the stripes but almost nothing else.
The supply comes in as a grid of wide straps on the upper layers, dropping through vias to the rails that run along every cell row. The spacing is a real design choice: closer straps mean less voltage drop and less routing resource left for signals. Two things in the drill are worth checking against this picture. The voltage map from this same run is banded, and the bands share this pitch, because how far a cell sits from a strap is most of what sets its drop. And the routing view of the same run is this picture with the supply nets switched off, which is the only difference between them.