Exploring the NEC V20 CPU
A V20 CPU, courtesy of Konstantin Lanzet ( CC ) The NEC V20 was a 16-bit CPU released in 1984. It is pin-compatible with the Intel 8088 , and clones the 8088's instruction set. It also includes newer instructions that had been introduced two years prior by the Intel 80186 and 80286 , but does not include the latter's protected-mode features. Besides the 186 instruction set, NEC also added new opcodes and instruction prefixes of their own, enabling performance enhancements for software that could detect or require a V20. NEC also incorporated various other improvements Intel had made in the 80186, namely hardware support for address calculation and for division and multiplication. The former was a big benefit overall, as it could decrease the execution time of any instruction utilizing a memory address operand. The V20 was one of the first 3rd-party, drop-in CPU replacements for the PC. An owner of an original IBM 5150 could pull the 8088 out of their motherboard's CPU so...