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In 1980, Intel announced the 8087 Math Coprocessor, a chip that made floating-point 100 times faster. I opened up the chip, took photos of the silicon structures, and analyzed its circuitry. It's a very complex chip for its time. Let's take a look inside...

Unlike most processors, the 8087 organizes its registers into a "stack", pushing numbers onto the top of the stack and popping them off. Here's a close-up of the eight registers, organized in a grid of cells. Each register holds an 80-bit number, so the registers are very tall.

Each bit is stored in a "static RAM" cell, consisting of two inverters in a loop. This circuit has two stable states, holding a 0 or a 1. The implementation is complicated: silicon with polysilicon lines on top to make transistors. Horizontal metal wires connect everything.

Intel was hesitant to produce the 8087 chip, considering it complex, risky, and with an unknown market. Intel's Israel site took on the project; the die is marked "i/IL". The chip was a highly profitable success. Now, almost all computers use floating-point systems based on the 8087.

Was it significantly different (and superior) in structure/concept/architecture to the floating point hardware of previous mini/mainframe/super computers?

For more on the stack circuitry in the 8087, see my blog post: www.righto.com/2025/12/8087...

Have you ever looked at the AMD 9511? This was licensed by Intel as well and sold as Intel 8231.