Ken Shirriff's reverse-engineering work on the Intel 8087 FPU reveals how conditional tests are implemented in microcode. The microcode engine acts as its own CPU, executing specialized floating-point instructions like cosine and arctangent. Conditional instructions are implemented in hardware using multiplexers and pass transistors, with evaluation performed close to the source to minimize wiring. Despite being obsolete, the 8087 provides valuable insights into ASIC design principles.
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