Reverse-Engineering a Pentium's Carry-Lookahead Adder
2025-01-18
Ken Shirriff's blog post details the reverse engineering of an 8-bit adder within the Pentium's floating-point unit. This adder, a Kogge-Stone carry-lookahead adder, accelerates addition by calculating carry bits in parallel. The post meticulously explains the carry-lookahead adder's principle, showcasing the Pentium's hardware implementation—a four-layer circuit structure employing the Kogge-Stone algorithm. It also discusses the adder's role in the Pentium's floating-point division unit and its connection to the infamous Pentium FDIV bug.
Hardware
carry-lookahead adder