Gecko's CPU Library

NEC V20 processors

Introduction: 1984

NEC V20 is a 16-bit CMOS microprocessor with 8-bit external data bus, object-code and pin-compatible with Intel 8088. The V20 runs at the same speed as the 8088, but it's slightly faster due to internal improvements - dual internal 16-bit data bus, faster effective address calculation, better loop counter/shift register implementation, and some others.

The V20 includes Intel 8080 emulation mode, in which it can execute all of the 8080 instructions. Native NEC V20 instruction set includes all 8086/8088 instructions, new instructions from the 80186/80188 microprocessor, and instructions unique to V20 - bit processing, packed BCD instructions and special instructions for switching the processor to 8080 emulation mode and back.

The V20 is almost the same as the NEC V30 with the exception that the V30 has 16-bit data bus.