Puzzle 86 of 100

Greater than

Goal

Make Y high while the number A1 A0 is greater than B1 B0. The majority gate and the inverter that drives Y are drawn.

Die: 37 by 22 squares
Layers: Metal, Polysilicon, Contact, N active, P active, N well, Metal 2, Via
Inputs: A0, B0, A1, B1
Output: Y
Supply: VDD
Ground: GND

New in this puzzle

Comparing from the top

The high bits decide a comparison unless they are equal, and then the low bits decide. The low result passes upward the way a carry does, so a majority gate combines it with the high bits.

Hint

Y is high while A1 is high and B1 is low, or while A1 equals B1 and the low bits give A0 high with B0 low. That is the majority of A1, the inverse of B1, and the low result. Make the low result with an inverter on A0 and a NOR gate, and invert B1.

Solution

This is the game's reference drawing for the puzzle. It meets the goal and passes the design rules. Other drawings can pass as well.

Top View of the solved die for puzzle 86, Greater than, with the Side View below it. — Top View of the solved die, captured from the game. Paths that carry a high level at the moment shown are lit. The Side View below cuts through the row between the dashed lines.

The game window in Isometric View with the solved die for puzzle 86, Greater than, the guide, and the scope. — The whole game window in Isometric View. The scope on the right compares each output with its target band, and the message above it confirms that the drawing passes.

Solution drawing for puzzle 86, Greater than, drawn on a numbered grid with every layer in its game color and pattern. — The solution on the grid. Squares are numbered from the top left corner, so you can count them. The dashed outline marks the squares you draw, change, or erase; the rest is drawn when the puzzle opens.

Legend

Metal236 squares
Polysilicon97 squares
Contact61 squares
N active38 squares
P active76 squares
N well185 squares
Metal 2174 squares
Via34 squares
Input padA0, B0, A1, B1
Output padY
Supply padVDD
Ground padGND
Squares you draw, change, or erase162 squares

About the drawing

The drawing uses 504 of the die's 814 squares.
Part of the drawing is in place when the puzzle opens. To finish it, paint 111 empty squares and change 51 drawn squares.
It forms 22 transistors: 11 N transistors and 11 P transistors. Each one is a place where polysilicon crosses active silicon.
61 contacts join metal to the polysilicon or active silicon under it.
34 vias join metal 2 to the metal under it.

Starting drawing for puzzle 86, Greater than, on a numbered grid. — The drawing when the puzzle opens. The dashed outline marks the squares the solution changes.