NEC V20
Encyclopedia
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
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 microprocessor was a variant of the Intel 8086 and was introduced on July 1, 1979. It had an 8-bit external data bus instead of the 16-bit bus of the 8086. The 16-bit registers and the one megabyte address range were unchanged, however...
with an instruction set
Instruction set
An instruction set, or instruction set architecture , is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O...
compatible with the Intel 80186
Intel 80186
The 80188 is a version with an 8-bit external data bus, instead of 16-bit. This makes it less expensive to connect to peripherals. The 80188 is otherwise very similar to the 80186. It has a throughput of 1 million instructions per second....
. 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). NEC V20 was used in "turbo" versions of some PC clones such as Commodore PC compatible systems
Commodore PC compatible systems
The Commodore PC compatible systems were a range of IBM PC compatible personal computers introduced in 1984 by home computer manufacturer Commodore Business Machines. Incompatible with Commodore's prior PET and Commodore 64 series, they were generally regarded as good, serviceable workhorse PCs...
, Copam, and Tandy
Tandy Corporation
Tandy Corporation was a family-owned leather goods company based in Fort Worth, Texas. Tandy was founded in 1919 as a leather supply store, and acquired RadioShack in 1963. The Tandy name was dropped in May 2000, when RadioShack Corporation was made the official name.-History:Tandy began in 1919...
1110 laptop series. It was also used in the Casio PV-S450 PDA and Hewlett-Packard's HP 95LX
HP 95LX
The HP 95LX was the first MS-DOS pocket computer or personal digital assistant, introduced by Hewlett-Packard in April 1991 in collaboration with Lotus Development Corporation....
. Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
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 the second 8-bit microprocessor designed and manufactured by Intel and was released in April 1974. It was an extended and enhanced variant of the earlier 8008 design, although without binary compatibility...
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 or return to or from the emulation mode. There was a V2080 CPMulatorCPMulator
CPMulator is a program to emulate the CP/M operating system under x86 DOS. The program was developed in 1984 by Keystone Software Development. The company was owned and operated by Jay Sprenkle....
program which allowed to run 8080-based CP/M-80
CP/M
CP/M was a mass-market operating system created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc...
programs on a MS-DOS machine.
Intel 8086
The 8086 is a 16-bit microprocessor chip designed by Intel between early 1976 and mid-1978, when it was released. The 8086 gave rise to the x86 architecture of Intel's future processors...
processor. It too supported the 8080 emulation mode. The V30 was used in the GTD-5 EAX
GTD-5 EAX
The GTD-5 EAX is the Class 5 telephone switch developed by GTE Automatic Electric Laboratories...
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 × 85 × 22 mm...
, in the NEC PC-9801, the Olivetti
Olivetti
Olivetti S.p.A. is an Italian manufacturer of computers, printers and other business machines.- Founding :The company was founded as a typewriter manufacturer in 1908 in Ivrea, near Turin, by Camillo Olivetti. The firm was mainly developed by his son Adriano Olivetti...
PCS86, 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.-History:...
"PC Transporter" emulator for the Apple II
Apple II
The Apple II is an 8-bit home computer, one of the first highly successful mass-produced microcomputer products, designed primarily by Steve Wozniak, manufactured by Apple Computer and introduced in 1977...
series of computers, and in various arcade machines (particularly ones made by Irem) in the late 1980s.
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 processor. Features include:* NEC V20 core: 8-bit external data path, 20-bit address bus* Timers* Internal interrupt controllerIt was officially phased out by NEC in...
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 80286 , introduced on 1 February 1982, was a 16-bit x86 microprocessor with 134,000 transistors. Like its contemporary simpler cousin, the 80186, it could correctly execute most software written for the earlier Intel 8086 and 8088...
. 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 (μPD70136A) differs from the NEC V33 in that it has interrupt vector numbers compatible with intel 80X86 processors.
Intel 8253
The Intel 8253 and 8254 are Programmable Interval Timers , which perform timing and counting functions. They were primarily designed for the Intel 8080/8085-processors, but later used in x86-systems...
programmable interval timer, and 8255
Intel 8255
The Intel 8255 Programmable Peripheral 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 MCS-85 Family. This chip was later also used with the Intel 8086 and its descendants.It was later...
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, PC XT, or simply XT, was IBM's successor to the original IBM PC. It was released as IBM Machine Type number 5160 on March 8, 1983, and came standard with a hard drive...
peripherals: 8255
Intel 8255
The Intel 8255 Programmable Peripheral 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 MCS-85 Family. This chip was later also used with the Intel 8086 and its descendants.It was later...
parallel port interface, 8254
Intel 8253
The Intel 8253 and 8254 are Programmable Interval Timers , which perform timing and counting functions. They were primarily designed for the Intel 8080/8085-processors, but later used in x86-systems...
programmable interval timer, 8259
Intel 8259
The Intel 8259 is a Programmable Interrupt Controller designed for the Intel 8085 and Intel 8086 microprocessors. The initial part was 8259, a later A suffix version was upward compatible and usable with the 8086 or 8088 processor...
PIC, 8237
Intel 8237
Intel 8237 is a direct memory access controller , a part of the MCS 85 microprocessor family. It was used as the DMA controller in the original IBM PC and IBM XT...
DMA controller and 8042 keyboard controller. Also integrates full DRAM controller. Was used in Olivetti
Olivetti
Olivetti S.p.A. is an Italian manufacturer of computers, printers and other business machines.- Founding :The company was founded as a typewriter manufacturer in 1908 in Ivrea, near Turin, by Camillo Olivetti. The firm was mainly developed by his son Adriano Olivetti...
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 were primarily designed for the Intel 8080/8085-processors, but later used in x86-systems...
) and interrupt controller (μPD71059/i8259
Intel 8259
The Intel 8259 is a Programmable Interrupt Controller designed for the Intel 8085 and Intel 8086 microprocessors. The initial part was 8259, a later A suffix version was upward compatible and usable with the 8086 or 8088 processor...
).
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 (CGA/AT&T640x400) with touch-plane supprt, keyboard matrix scanner, dual PCMCIA 2.1 card controller, EMS
Expanded memory
In DOS memory management, expanded memory is a system of bank switching introduced April 24, 1985 that provided additional memory to DOS programs beyond the limit of conventional memory. Expanded memory uses parts of the address space normally dedicated to communication with peripherals for program...
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 and 120.
The enhanced Vadem VG330 contained a 32 MHz NEC V30MX processor and IBM PC/AT-compatible core logic with dual PICs, LCD controller (640x480), keyboard matrix scanner, PC Card
PC Card
In computing, PC Card is the form factor of a peripheral interface designed for laptop computers. The PC Card standard was defined and developed by the Personal Computer Memory Card International Association which itself was created by a number of computer industry companies in the United States...
ExCA 2.1 controller and SIR port.
Starting with the NEC V60
NEC V60
The NEC V60 was a CISC 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. A relatively obscure design, it was a radical departure from NEC's previous V-series CPUs , most of which were based on the Intel x86...
, NEC departed from the x86 design.
External links
V20