NEC V20

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NEC V20

The NEC V20 (µPD70108) was a processor

Central processing unit

A central processing unit is an electronic circuit that can execute computer programs. This broad definition can easily be applied to many early computers that existed long before the term "CPU" ever came into widespread usage....
made by NEC that was a reverse-engineered

Reverse engineering

Reverse engineering is the process of discovering the technological principles of a device, object or system through analysis of its structure, function and operation....
, pin-compatible version of the Intel 8088

Intel 8088

The Intel 8088 is an Intel x86 microprocessor based on the Intel 8086, with 16-bit registers and an 8-bit external data bus. It can address up to 1 megabyte of random access memory....
with an instruction set

Instruction set

An instruction set is a list of all the instruction , and all their variations, that a processor can execute.Instructions include:* Arithmetic such as add and subtract...
compatible with the Intel 80186

Intel 80186

The 80186 is a microprocessor that was developed by Intel circa 1982. The 80186 was an improvement on the Intel 8086 and Intel 8088. As with the 8086, it had a 16-bit external bus and was also available as the Intel 80188, with an 8-bit external data bus....
. The chip featured approximately 29,000 transistors, 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).

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Encyclopedia

The NEC V20 (µPD70108) was a processor

Central processing unit

Reverse engineering

Intel 8088

Instruction set

Intel 80186

Tandy Corporation

Tandy Corporation was a family-owned leather goods company based in Fort Worth, Texas, which is best known for purchasing and giving its name to the Fort Worth, Texas-based RadioShack....
1110 laptop series. Also used in the Casio PV-S450 PDA. Sony

Sony

is a multinational corporation list of conglomerates corporation headquartered in Minato, Tokyo, Japan, and one of the world's largest media conglomerates with revenue exceeding US$99.1 billion ....
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

Intel 8080

The Intel 8080 was an early microprocessor designed and manufactured by Intel. The 8-bit microprocessor was released in April 1974 running at 2 megahertz , and is generally considered to be the first truly usable microprocessor....
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

CP/M

CP/M is an operating system originally created for Intel 8080/Intel 8085 based microcomputers by Gary Kildall of Digital Research. Initially confined to single tasking on 8-bit processors and no more than 64 kilobytes of memory, later versions of CP/M added multi-user variations, and were migrated to 16-bit processors....
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

Intel 8086

The 8086 is a 16-bit microprocessor chip designed by Intel and introduced on the market in 1978, which gave rise to the x86 architecture. Intel 8088, released in 1979, was essentially the same chip, but with an external 8-bit bus , and is notable as the processor used in the original IBM PC....
processor. It was used in the GTD-5 EAX

GTD-5 EAX

The GTD-5 EAX is the Class 5 telephone switch telephone switch developed by GTE Automatic Electric Laboratories. This digital central office telephone circuit switching system is used in the former GTE service areas and by many smaller telecommunications service providers....
Class 5 central office as a drop-in performance upgrade for the processor complex in the late 1980s. It was also used in the Psion Series 3

Psion 3

The Psion Series 3 range of personal digital assistants were made by Psion PLC. The four main variants are the Psion Series 3 , the Psion Series 3a , the Psion Series 3c , and the Psion Series 3mx , all sized 165 x 85 x 22 mm....
, in the NEC PC-9801, the Applied Engineering

Applied Engineering

Applied Engineering, headquartered in Carrollton, TX, was a leading third-party hardware vendor for the Apple II series of computers from the early 1980s until the mid-1990s....
"PC Transporter" emulator for the Apple II series of computers, 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
NEC V25

The NEC V25 is the microcontroller version of the NEC V20 CPU. Features include:* NEC V20 core: 8-bit external data path, 20-bit address bus* Timers...
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

Intel 80286

The Intel 286, introduced on February 1, 1982, was an x86 16-bit microprocessor with 134,000 transistors.It was widely used in IBM PC compatible computers during the mid 1980s to early 1990s....
. 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 emulation mode was not supported.

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

NEC V40 (µPD70208) embedded version of V20, integrated Intel-compatible 8251 USART, 8253

Intel 8253

The Intel 8253 and 8254 are Programmable Interval Timers , which perform timing and counting functions. They are found in all x86 PCs....
programmable interval timer, and 8255

Intel 8255

The Intel 8255 Programmable Peripheral Physical interface chip is a peripheral chip originally developed for the Intel 8085 microprocessor, and as such is a member of a large array of such chips, known as the Intel 8085#MCS-85 Family....
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

IBM Personal Computer XT

The IBM Personal Computer XT, often shortened to the IBM XT or simply XT, was IBM's successor to the original IBM Personal Computer....
peripherals: 8255

Intel 8255

Intel 8253

The Intel 8253 and 8254 are Programmable Interval Timers , which perform timing and counting functions. They are found in all x86 PCs....
programmable interval timer, 8259

Intel 8259

The Intel 8259 is a family of Programmable Interrupt Controllers designed and developed for use with the Intel 8085 and Intel 8086 8-bit and 16-bit microprocessors....
PIC, 8237

Intel 8237

An Intel chipset to help transferring data from peripheral devices to and from system memory without occupying CPU....
DMA controller and 8042 keyboard controller. Also integrates full DRAM controller. Was used in Olivetti

Olivetti

Ing. C. Olivetti & Co., SpA., known as Olivetti, is an Italy manufacturer of computers, computer printers and other business machines....
Quaderno XT-20.

The NEC V53 (µPD70236) integrates a V33 core with 4-channel DMA (µPD71087/i8237), UART (µPD71051/i8251), three timer/counters (µPD71054/i8254

Intel 8253

The Intel 8253 and 8254 are Programmable Interval Timers , which perform timing and counting functions. They are found in all x86 PCs....
) and interrupt controller (µPD71059/i8259

Intel 8259

The Intel 8259 is a family of Programmable Interrupt Controllers designed and developed for use with the Intel 8085 and Intel 8086 8-bit and 16-bit microprocessors....
).

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

PC card

In computing, PC Card is the form factor of a peripheral interface designed for laptop computers. The PC Card standard were defined and developed by a group of industry-leading companies called the Personal Computer Memory Card International Association ....
controller. Was used in the HP OmniGo 100

HP 200Lx

The HP 200LX is a personal digital assistant introduced by Hewlett-Packard in 1994. It was often called a palmtop computer, and it was notable that it was, with some minor exceptions, a MS-DOS compatible computer in a palmtop format, complete with a monochrome graphic display, qwerty keyboard, serial port, and PCMCIA expansion slot....
.

Starting with the NEC V60

NEC V60

The NEC V60 was a Complex instruction set computer processor manufactured by NEC introduced in the late 1980s. It had a 32-bit internal bus and a 16-bit external bus with a 24-bit address bus....
, NEC departed from the x86 design.

External links

V20