Reverse-engineering the vintage Intel 8087's tangent algorithm: more than CORDIC
Summary
Ken Shirriff's deep dive documents how Intel's 8087 tangent instruction is implemented using a hybrid of CORDIC and a rational Padé approximation. The post details the microcode, hardware paths, and fixed-point-like arithmetic, and it situates the approach within historical context and later shifts in Intel's math hardware. This is a valuable resource for understanding hardware-based trig computation and retrocomputing reverse-engineering techniques.