Ken Shirriff @righto.com · Jun 13 I dissolved the metal with acid so you can see the silicon circuits in the 8087 chip. The pinkish regions are doped silicon. The thin lines are polysilicon wires on top of the silcon. When polysilicon crosses doped silicon, it forms a transistors, the switches that make circuits work.
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The adder is part of a set of registers and shifters that make multiplication, division, and square roots fast. The 8087 multiplies two bits at a time (twice as fast) thanks to the Multiply Decision Box and selector. The Quotient Register is for division. Square roots get bits from the Skip Shifter.