Die-analysis

Ken Shirriff's post reverse-engineers the 8087 FXCH microcode, revealing detailed micro-instruction flow, ROM size, and die architecture.

Reverse-engineering the Intel 8087 reveals an eight-entry, 80-bit stack with push/pop rules, a carry-lookahead adder and toggle-based increment/decrement, plus a dense, multi-layer RAM-like register file and a semi-analog microcode ROM; the design produced stack overflow/underflow pitfalls that affected compiler and OS support, and was eventually superseded by SSE/AVX.