NEC V20

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NEC V20

The NEC V20 (μPD70108) was a processor made by NEC that featured approximately 29,000 transistors. It was a reversed-engineered, pin-compatible version of the Intel 8088 with an instruction set compatible with the Intel 80186. The chip ran at 8 to 16 MHz and was around 30% faster (application dependent) than the 8088 at the same clock speed, primarily due to a hardware multiplier (whereas the 8088 had to perform multiplication using a microcode program). NEC V20 was used in "turbo" versions of some PC clones such as Copam and Tandy 1110 laptop series. Also used in the Casio PV-S450 PDA. Sony also produced this microprocessor under license from NEC as the V20H (Sony CXQ70108).

An unusual feature of the NEC V20 was that it added an Intel 8080 emulation mode, in which it could execute programs written for the Intel 8080 processors. The instructions BRKEM executed in 8086 mode (NEC used a different notation for the instructions than Intel and BRK in NEC notation = INT in Intel notation) and RETEM and CALLN executed in 8080 mode was used to switch/return to/from the emulation mode. There was a V2080 CPeMulator program which allowed to run 8080-based CP/M-80 programs on a MS-DOS machine.

The NEC V30 (μPD70116) was a version of the NEC V20 that was pin compatible with the 16-bit data bus Intel 8086 processor. It was used in the GTD-5 EAX Class 5 central office as a drop-in performance upgrade for the processor complex in the late 1980s. Was also used in the Psion Series 3 and in various arcade machines (particularly ones made by Irem) in the late 1980's.

The NEC V20HL (μPD70108H) and NEC V30HL (μPD70116H) were a high-speed (up to 16MHz) and low-power versions.

The NEC V25 is the microcontroller version of the NEC V20 processor.

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 has two additional instructions BRKXA and RETXA to support extended addressing mode. The emulation mode was not supported.

The NEC V33A (μPD70136A) differs from the NEC V33 in that is has interrupt vector number compatible with intel 80X86 processors

NEC V40 (μPD70208) embedded version of V20, integrated Intel-compatible 8251 serial UART, 8253 programmable interval timer and 8255 parallel port interface. Used in the Olivetti PC1.

NEC V50 (μPD70216) embedded version of V30 with 16-bit data bus

The NEC V41 (μPD70270) NEC V51 (μPD70280) integrated V30HL core and PC-XT peripherals: 8255 parallel port interface, 8254 programmable interval timer, 8259 PIC, 8237 DMA controller and 8042 keyboard controller. Also integrates full DRAM controller. Was used in Olivetti Quaderno XT-20.

The NEC V53 integrates some peripherals with a V33 core.

The NEC V53A (μPD70236A) integrates some peripherals with a V33A core.

The Vadem VG230 was a single-chip PC platform. The VG230 contained 16-MHz NEC V30HL processor and IBM PC XT core logic, LCD controller, keyboard matrix scanner and PC Card controller. Was used in the HP OmniGo 100.

Starting with the NEC V60, NEC departed from the x86 design.