Reverse-engineering the vintage Intel 8087's tangent algorithm: more than CORDIC

· Ken Shirriff · Sept. 26, 2026, 4:35 p.m.
Summary
This blog post delves into the intricate workings behind the tangent algorithm of Intel's vintage 8087 floating-point chip, detailing its use of CORDIC and polynomial approximation for efficiency and accuracy. Through a blend of historical context and technical insights, the author analyzes the microcode and hardware features that enable quick tangent calculations.
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