The NEC V20 was a processor made by NEC that was a reverse-engineered, pin-compatible version of the Intel 8088 with an instruction set compatible with the Intel 80186. The V20 was introduced in 1982, and the V30 debuted in 1983. The chip featured much more than the 29,000 transistors of the simpler 8088 CPU, ran at 5 to 10 MHz.
Features
An unusual feature was the existence of several families of unique instructions. The ADD4S, SUB4S, and CMP4S instructions were able to add, subtract, and compare huge packed binary-coded decimal numbers stored in memory. Instructions ROL4 and ROR4 rotate four-bit nibbles. Another family consisted of the TEST1, SET1, CLR1, and NOT1 instructions, which test, set, clear, and invert single bits of their operands, but are far less efficient than the later i80386 equivalents BT, BTS, BTR, and BTC; neither are their encodings compatible. There were two instructions to extract and insert bit fields of arbitrary lengths. And finally, there were two additional repeat prefixes, REPC and REPNC, which amended the original REPE and REPNE instructions and allowed a string of bytes or words to be scanned while a less or not less condition remained true.
The NEC V33 is a super version of the V30 that separates address bus and data bus, and executes all instructions with wired logic instead of micro-codes, making it twice as fast as a V30 for the same clock frequency. V33 has the performance equivalent to Intel 80286. NEC V33 offers a method to expanding the memory address space to 16M bytes. It has two additional instructions BRKXA and RETXA to support extended addressing mode. The 8080 emulation mode was not supported.
The NEC V33A differs from the NEC V33 in that it has interrupt vector numbers compatible with intel 80X86 processors.
The NEC V35 is the microcontroller version of the NEC V30 processor. Has 16-bit external data bus.
NEC V50 embedded version of V30 with 16-bit data bus. It is the main CPU of the Korg M1.
NEC V50HL high-speed low-voltage version of V50
The NEC V41NEC V51 integrated V30HL core and PC-XT peripherals: 8255 parallel port interface, 8254 programmable interval timer, 8259 PIC, 8237DMA controller and 8042keyboard controller. Also integrates full DRAM controller. Was used in Olivetti Quaderno XT-20.
The NEC V53 integrates a V33 core with 4-channel DMA, UART, three timer/counters and interrupt controller.
The NEC V53A integrates some peripherals with a V33A core.
NEC V55PI
The Vadem VG230 was a single-chip PC platform. The VG230 contained a 16 MHz NEC V30HL processor and IBM PC/XT-compatible core logic, LCD controller with touch-plane support, keyboard matrix scanner, dual PCMCIA 2.1 card controller, EMS 4.0 hardware support for up to 64 MB, and built-in timer, PIC, DMA, UART and RTC controllers. It was used in the HP OmniGo 100, 120 and IBM Simon.
The enhanced Vadem VG330 contained a 32 MHz NEC V30MX processor and IBM PC/AT-compatible core logic with dual PICs, LCD controller, keyboard matrix scanner, PC Card ExCA 2.1 controller and SIR port.
Starting with the NEC V60, NEC departed from the x86 design.
