Counts and the cell mix
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 9 summaries in this family, with their numbers
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gcd on Nangate45, 45 nanometre: Is the final cell count over 1000?1086 cells, so over
The netlist had 521 instances and the layout holds 1086. The difference is 458 filler cells, 48 well taps, 68 buffers added by timing repair, and the clock tree. A cell count quoted without saying which stage it came from can be out by a factor of two.
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gcd on Nangate45, 45 nanometre: Are more than 500 of those cells filler?458 filler cells, so under
Filler is 458 cells, 42 percent of the count, and contributes no logic. It exists to keep the rows continuous, and the emptier the design, the more of it there is. This is why counting cells is a poor measure of a design and why area and utilization are quoted instead.
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gcd on Nangate45, 45 nanometre: Did the clock tree need more than 10 buffers?5 clock buffers, so under
Five buffers, two deep at the shallowest point, for 35 registers. A tree is mostly about balance rather than drive at this scale, and a block this small barely needs levels at all. The count grows with sinks, but much more slowly than one to one.
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aes on Nangate45, 45 nanometre: Did this clock tree need more than 150 buffers?107 clock buffers, so under
107 buffers for 562 sinks is about one for every five, against one for every seven on the small block, so the tree grew a little faster than the sink count but nothing like as fast as a guess of one per register would suggest. The minimum depth went from two levels to three.
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aes on Nangate45, 45 nanometre: Did timing repair insert more than 1000 buffers?3771 repair buffers, so over
3771 buffers, a third as many as the cells doing the logic. On a design pushed for speed, repair is not a finishing touch: it is a large part of what ends up on the die, and it is the first place to look when the area comes back bigger than synthesis promised.
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gcd, the same source file on sky130 high density, 130 nanometre: Does it synthesize to more than 400 instances here?222 instances, so under
222 against 521, from identical source. A relaxed clock target needs less parallel structure, and a different library maps the same logic onto different cells. Comparing two platforms is never comparing one design: it is comparing two netlists that happen to share a source file.
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ibex on Nangate45, 45 nanometre: Did this clock tree need more than 300 buffers?424 clock buffers, so over
424 buffers for 1938 registers, about one for every 4.6, continuing a trend from one in seven on the small block. Bigger designs need more levels and longer runs, so the tree grows faster than the sink count. At 509 square micrometres it is 1.7 percent of the cell area, and a good deal more of the power.
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jpeg on Nangate45, 45 nanometre: Are there more than 10000 inverters in the layout?12618 inverters, so over
12618 inverters, over a third as many as the combinational cells that do the work, plus 5358 repair buffers and 934 clock buffers on top. A large fraction of a finished design exists only to carry signals far enough, fast enough, which is the same story as wire length told in cells.
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aes, the same source as the Nangate45 run on sky130 high density, 130 nanometre: Does this version have more than 700 registers?562 registers, so under
562 on both platforms, exactly. Registers are written in the source, so the count survives any library and any target: what changes between platforms is the combinational logic, which the mapper rebuilds from scratch. The register count is one of the few numbers that travels.