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NEC V20

(Redirected fromVadem VG230)

TheNEC V20is amicroprocessorthat was designed and produced byNEC.It is bothpin compatibleandobject-code compatiblewith theIntel 8088,with aninstruction set architecture(ISA) similar to that of theIntel 80188with some extensions.[2]The V20 was introduced in March 1984.[1][2]

NEC V20 (μPD70108)
8 MHz V20 in plastic DIP package
General information
LaunchedMarch 1984;40 years ago(1984-03)[1]
Common manufacturers
Performance
Data width16 bits
Physical specifications
Transistors
  • 63000
Cores
  • 1
Co-processor
  • Intel 8087
  • NEC μPD72091
History
SuccessorNEC V60

Features

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The V20'sdiecomprised 63,000transistors;more than double the 29,000 of the 8088 CPU.[1]The chip was designed for a clockduty cycleof 50%, compared to the 33% duty cycle used by the 8088.[3]The V20 has two 16-bit wide internal databuses, allowing two data transfers to occur concurrently.[4]Differences like that meant that a V20 could typically complete more instructions in a given time than an Intel 8088 running at the same frequency.[2]

The V20 was fabricated in 2-micron CMOS technology.[5][3]Early versions ran at speeds of 5, 8, and 10MHz.[6]: 2 In 1990, an upgrade to the fabrication process technology resulted in the V20H and V20HL, with improved performance and reduced power consumption.[5]Later versions added speeds of 12 and 16 MHz. The V20HLs were also completely static, allowing their clock to be stopped.

The V20 was described as16-bitswide internally. It used an 8-bit external data bus that was multiplexed onto the same pins as the low byte of the address bus. Its 20-bit wide address bus was able to address 1 MB of memory.

The V20 was reported to have been compatible with the Intel 8087floating-point unit(FPU) coprocessor.[7]NEC also designed their own FPU, theμPD72091[jp],which was cancelled before reaching production. They followed this with a revised design, the μPD72191, but it is unclear how many, if any, of this second part were produced.[8]

The V30, a nearly identical CPU with a 16-bit wide external data bus, debuted on March 1, 1984.[9][5]It was pin and object-code compatible with the Intel 8086.

ISA extensions

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Sony CXQ70108D 8 MHz

The V20's ISA includes several instructions not executed by the 8088, with instructions for bit manipulation, packed BCD operations, multiplication, and division. They also include new real-mode instructions from the Intel 80286.[10]

TheADD4S,SUB4S,andCMP4Sinstructions were able to add, subtract, and compare huge packedbinary-coded decimalnumbers stored in memory. InstructionsROL4andROR4rotate four-bitnibbles.Another family consisted of theTEST1,SET1,CLR1,andNOT1instructions, which test, set, clear, and invert single bits of their operands, but are far less efficient than the lateri80386equivalentsBT,BTS,BTR,andBTC;neither are their encodings compatible. There were two instructions to extract and insert bit fields of arbitrary lengths (EXT,INS). And finally, there were two additional repeat prefixes,REPCandREPNC,which amended the originalREPEandREPNEinstructions for scanning a string of bytes or words (with instructionsSCASandCMPS) while a less or not less condition remained true.[11]

The V20 offered a mode that emulated anIntel 8080CPU. ABRKEMinstruction is issued to start 8080 emulation. The operand of the instruction specifies an interrupt number whose vector contains the segment:offset where emulation is to begin. To end, aRETEMinstruction is issued in 8080 code. One feature not often employed is theCALLN(call native) which issues an 8086-type interrupt call that enables x86 code (which returns using anIRET) to be mixed in with 8080 code.

Another mode put the processor into a power-saving state via aHALTinstruction.[6][7]

Lawsuits

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In 1982, Intel sued NEC over the latter's μPD8086 and μPD8088. This suit was settled out of court, with NEC agreeing to license the designs from Intel.[12]

In late 1984, Intel again filed suit against NEC, claiming that the microcode in the V20 and V30 infringed its patents for the 8088 and 8086 processors.[13]NEC software engineer Hiroaki Kaneko had studied both the hardware design of the Intel CPUs and the original Intel microcode.

In its ruling, the court determined that the microcode in the control store constitutes a computer program, and so is protected by copyright.[14]They further found Intel to have forfeited their copyright by neglecting to ensure that all second-source chips were suitably marked. The court also determined that NEC did not simply copy Intel's microcode, and that the microcode in the V20 and V30 was sufficiently different from Intel's to not infringe Intel's patents.

The judge in the case accepted NEC'scleanroomevidence. He also approved of NEC's use ofreverse engineeringwith respect to the creation of NEC's Rev.2 microcode, without commenting on it with respect to the Rev.0 code.[14]: 212–221 

Variants and successors

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V20 on a motherboard
NEC V30 (μPD70116), 10 MHz
NEC V33A (μPD70136AL)
NEC V40 (μPD70208)
NEC V53A (μPD70236A)
Product Part no. Details
NEC V30 μPD70116 Essentially an NEC V20 with a 16-bit external data bus, the V30 was pin compatible with theIntel 8086.The V30 was a factory upgrade from the 8086 used in theGTD-5 EAXClass 5 central office switch. It was also used in thePsion Series 3,theNEC PC-9801VM, theOlivettiPCS86, theApplied Engineering"PC Transporter" card for theApple IIseries of computers, and in various arcade machines (particularly ones made byIrem) in the late 1980s. Years later, a low-voltage V30 MZ version was used inBandai's handheldWonderSwangame console.
NEC V20HL μPD70108H High-speed (up to 16 MHz), low-power version of the V20.
NEC V30HL μPD70116H High-speed (up to 16 MHz), low-power version of the V30.
NEC V25 μPD70320 Amicrocontrollerversion of the NEC V20.
NEC V25HS μPD79011 A version of the V25 with theRX116RTOS in the internal ROM.
NEC V25+ μPD70325 High-speed version of the V25.
NEC V33 μPD70136 A version of the V30 with separate address and data buses and with instruction decode done by hardwired logic rather than a microprogrammed control store. Throughput is twice as high as a V30 for the same clock frequency. The V33 has performance equivalent toIntel 80286.Memory address space is increased to 16M bytes. Two additional instructions,BRKXAandRETXA,support the extended addressing mode. 8080 emulation is not supported.
NEC V33A μPD70136A Differs from the V33 in that it has interrupt vector numbers compatible with Intel's 80X86 processors.
NEC V35 μPD70330 A microcontroller version of the NEC V30.
NEC V35HS μPD79021 A version of the V35 with the RX116 RTOS in the internal ROM.
NEC V35+ μPD70335 A high-speed version of the V35.
NEC V40 μPD70208 An embedded version of the V20, integrated Intel-compatible8251USART,8253programmable interval timer, and8255parallel port interface. Used in the Olivetti PC1, Digisystems Jetta XD, theSharp PC-4500and theZenith Eazy PC.
NEC V40HL μPD70208H A high-speed, low-voltage version of the V40.
NEC V50 μPD70216 An embedded version of the V30. It is the main CPU in theAkai S1000and S1100, and theKorg M1.[15][16]
NEC V50HL μPD70216H A high-speed, low-voltage version of the V50.
NEC V41 μPD70270 Integrates a V30HL core andPC-XTperipherals:8255parallel port interface,8254programmable interval timer,8259PIC,8237DMAcontroller and8042keyboard controller. Also integrates full DRAM controller.
NEC V51 μPD70280 Integrates a V30HL core andPC-XTperipherals:8255parallel port interface,8254programmable interval timer,8259PIC,8237DMA controller and8042keyboard controller. Also integrates full DRAM controller. Was used in theOlivetti QuadernoPT-XT-20.
NEC V53 μPD70236 Integrates a V33 core with 4-channel DMA (μPD71071[17]/i8237),UART(μPD71051/i8251), three timer/counters (μPD71054/i8254) andinterrupt controller(μPD71059/i8259). It was used in theAkai MPC3000[18][19]andAkai SG01v.
NEC V53A μPD70236A Integrates some peripherals with a V33A core. Used inSharp Zaurus PI-B304/B308
NECV55PI[jp] μPD70433 The V55PI has extended segment registers called DS2 and DS3, and by shifting the register value by 8 bits to the left and adding an offset value, it is possible to access the entire 16MB address space.[20]
NEC V55SC μPD70423 The V55SC not only comes with extended segment registers, called DS2 and DS3, but is also furnished with a two-channel Multi Protocol Serial Controller (MPSC) which is subset of μPD72001/72002.[21]
VademVG230 A single-chip PC platform.[22]The VG230 contained a 16 MHz NEC V30HL processor and IBM PC/XT-compatible core logic, LCD controller (CGA/AT&T640x400) with touch-plane support, keyboard matrix scanner, dualPCMCIA2.1 card controller,EMS4.0 hardware support for up to 64 MB, and built-in timer, PIC, DMA, UART and RTC controllers. It was used in theHP OmniGo 100,120andIBM Simon.[23]
VademVG330 Successor to the VG230, it contained a 32 MHz NEC V30MX processor and IBM PC/AT-compatible core logic with dual PICs, LCD controller (640x480), keyboard matrix scanner,PC CardExCA 2.1 controller and SIR port.
NEC V60 μPD70616 With the V60 processor, NEC departed from the x86 design and launched a new, 32-bitCISCarchitecture. The V60 and the V70, which differed mainly in the widths of their respective external address and data busses, both included a V20/V30 emulation mode.[24]: §10 [8]
  • Die photos
  • NEC V30
  • NEC V50
  • NEC V53

See also

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References

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  1. ^abc"8088 & V20".X86 CPU's Guide.2018-11-17.
  2. ^abcGennadiy, Shvets."NEC V20 processor family".CPU-World.
  3. ^abDavis, Stephen R. (1985-12-24). "Turbocharging Your PC with the V-Series".PC Magazine.pp. 181–186.
  4. ^Chodorek, Robert Ryszard (November–December 2021)."NEC V20: Inspiring, Inconspicuous".IEEE Micro.41(6): 158–159.doi:10.1109/MM.2021.3115870.
  5. ^abc1983 niên — 16bitマイクロプサッサV30の khai phát (NEC)[1983 — Development of the V30 16-bit Microprocessor (NEC)] (in Japanese). 2010-10-23. Archived fromthe originalon 2019-07-13.Retrieved2020-07-14.
  6. ^abμPD70108 — V20 16-/8-bit Microprocessor(PDF).NEC.June 1994.
  7. ^abMahoney, Bob (1985-10-16)."Output of file: NECV20B.ALL contained in archive: NEC-V20.ZIP".The Programmer's Corner.
  8. ^abCulver, John (2021-09-01)."NEC's Forgotten FPUs".The CPU Shack.
  9. ^"Nec V30 D70116C-10".X86 CPUS' GUIDE.2020-07-15.
  10. ^Hummel, Robert L. (1988-06-14). "PC Tutor — Mixing Processors".PC Magazine.pp. 377–378.
  11. ^"NEC User's Manual, 16-Bit V Series, 16-/8- and 16-bit microprocessors, Instruction"(PDF).September 2000.Retrieved2014-11-25.
  12. ^Lemos, Robert (1998-06-08)."NEC case opened up market for cloning".ZDNet.
  13. ^Parker, Rachel (1989-02-13). "Judge Declares Microcode Copyrightable".InfoWorld.p. 8.
  14. ^abContreras, Jorge; Handley, Laura; Yang, Terrence (March–May 1990)."NEC v. Intel: Breaking New Ground in the Law of Copyright"(PDF).Harvard Journal of Law and Technology.3:209–222.
  15. ^Korg M1 Service Manual
  16. ^Russ, Martin (July 1989)."Korg M1R".Sound On Sound.United Kingdom. pp. 48–52.Retrieved2022-08-13.
  17. ^"pPD70236 (V53) 16-Bit Microprocessor: High-Speed, High-Integration, CMOS"(PDF).p. 316(3f1).Retrieved2024-01-05.
  18. ^"Mame/Mpc3000.CPP at 251b11266dcd394741e6b48c00a5c9131ef68673 · mamedev/Mame".GitHub.2022-11-23.
  19. ^"AKAI MPC 3000: The Best Drum Machine of All Time".Audio Jive.2020-12-09.
  20. ^"V55PI 16-BIT MICROPROCESSOR".pp. 21–22.Retrieved2024-01-18.
  21. ^"NEC V55SC 16-bit Microprocessor Preliminary Data Sheet (O.D.No ID-8206A, March 1993)"(PDF).pp. 1, 22.Retrieved2024-01-21.
  22. ^Vadem VG230 Developer's Manual
  23. ^Nochkin, Alexander (2013-07-10)."IBM Simon — первый в мире смартфон. Что внутри?"[The IBM Simon is the world's first smartphone. What is inside?].habr.com(in Russian).
  24. ^μPD70616 Programmer's Reference Manual(PRELIMINARY ed.). NEC. November 1986.

Further reading

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