A report on Accumulator (computing)

Walther WSR-16 mechanical calculator. The row of digit-wheels in the carriage (at the front), is the Accumulator.
Front panel of an IBM 701 computer with lights displaying the accumulator and other registers

Register in which intermediate arithmetic logic unit results are stored.

- Accumulator (computing)
Walther WSR-16 mechanical calculator. The row of digit-wheels in the carriage (at the front), is the Accumulator.

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Processor register

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Quickly accessible location available to a computer's processor.

Quickly accessible location available to a computer's processor.

Data registers can hold numeric data values such as integer and, in some architectures, floating-point values, as well as characters, small bit arrays and other data. In some older and low-end CPUs, a special data register, known as the accumulator, is used implicitly for many operations.

The x86 architectures were based on the Intel 8086 microprocessor chip, initially released in 1978.

X86

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Family of complex instruction set computer instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant.

Family of complex instruction set computer instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant.

The x86 architectures were based on the Intel 8086 microprocessor chip, initially released in 1978.
Intel Core 2 Duo, an example of an x86-compatible, 64-bit multicore processor
AMD Athlon (early version), a technically different but fully compatible x86 implementation
Am386, released by AMD in 1991
Registers available in the x86-64 instruction set
In supercomputer clusters (as tracked by TOP 500 data and visualized on the diagram above, last updated 2013), the appearance of 64-bit extensions for the x86 architecture enabled 64-bit x86 processors by AMD and Intel (teal hatched and blue hatched, in the diagram, respectively) to replace most RISC processor architectures previously used in such systems (including PA-RISC, SPARC, Alpha, and others), and 32-bit x86 (green on the diagram), even though Intel initially tried unsuccessfully to replace x86 with a new incompatible 64-bit architecture in the Itanium processor. The main non-x86 architecture which is still used, as of 2014, in supercomputing clusters is the Power ISA used by IBM Power microprocessors (blue with diamond tiling in the diagram), with SPARC as a distant second.

For example, using AL as an accumulator and adding an immediate byte value to it produces the efficient add to AL opcode of 04h, whilst using the BL register produces the generic and longer add to register opcode of 80C3h.

One instruction may have several fields, which identify the logical operation, and may also include source and destination addresses and constant values. This is the MIPS "Add Immediate" instruction, which allows selection of source and destination registers and inclusion of a small constant.

Instruction set architecture

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Instruction set architecture , also called computer architecture, is an abstract model of a computer.

Instruction set architecture , also called computer architecture, is an abstract model of a computer.

One instruction may have several fields, which identify the logical operation, and may also include source and destination addresses and constant values. This is the MIPS "Add Immediate" instruction, which allows selection of source and destination registers and inclusion of a small constant.

1-operand (one-address machines), so called accumulator machines, include early computers and many small microcontrollers: most instructions specify a single right operand (that is, constant, a register, or a memory location), with the implicit accumulator as the left operand (and the destination if there is one):, ,.

An Intel C8080A processor variant with white ceramic package, solder seal metal lid, and gold pins.

Intel 8080

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Second 8-bit microprocessor designed and manufactured by Intel.

Second 8-bit microprocessor designed and manufactured by Intel.

An Intel C8080A processor variant with white ceramic package, solder seal metal lid, and gold pins.
i8080 microarchitecture
8080 Pinout
AMD Am9080
CEMI MCY7880 (Poland)
Kvazar Kiev K580IK80 (Soviet Union)
Mitsubishi Electric M5L8080
National Semiconductor INS8080
NEC μPD8080AF
OKI MSM8080
Siemens SAB8080
Signetics MP8080
Tesla (Czechoslovak company) MHB8080
Texas Instruments TMS8080

All 8-bit operations with two operands can only be performed on the 8-bit accumulator (the A register).

Part of the first IBM 650 computer in Norway (1959), known as "EMMA". 650 Console Unit (right, an exterior side panel is open), 533 Card Read Punch unit (middle, input-output). 655 Power Unit is missing. Punched card sorter (left, not part of the 650). Now at Norwegian Museum of Science and Technology in Oslo.

IBM 650

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Early digital computer produced by IBM in the mid-1950s.

Early digital computer produced by IBM in the mid-1950s.

Part of the first IBM 650 computer in Norway (1959), known as "EMMA". 650 Console Unit (right, an exterior side panel is open), 533 Card Read Punch unit (middle, input-output). 655 Power Unit is missing. Punched card sorter (left, not part of the 650). Now at Norwegian Museum of Science and Technology in Oslo.
Part of the first IBM 650 computer in Norway (1959), known as "EMMA". 650 Console Unit (right, an exterior side panel is open), 533 Card Read Punch unit (middle, input-output). 655 Power Unit is missing. Punched card sorter (left, not part of the 650). Now at Norwegian Museum of Science and Technology in Oslo.
IBM 650 at Texas A&M University. The IBM 533 Card Read Punch unit is on the right.
IBM 650 console panel, showing bi-quinary indicators. (At House for the History of IBM Data Processing (closed), Sindelfingen)
Close-up of bi-quinary indicators
Memory drum from an IBM 650
Side view of an IBM 650 Console Unit. First computer in Spain (1959) now at National Museum of Science and Technology in A Coruña
IBM 650 at Texas A&M, opened up to show rear of front panel, vacuum tube modules and storage drum
Vacuum tube circuit module of type used in the 650
A classroom in 1960 at the Bronx High School of Science with IBM 650 instruction chart above blackboard, upper right

Data read from the drum went through a 10-digit distributor. The 650 had a 20-digit accumulator, divided into 10-digit lower and upper accumulators with a common sign.

A MOS Technology 6502 processor in a DIP-40 plastic package. The four-digit date code indicates it was made in the 45th week (November) of 1985.

MOS Technology 6502

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8-bit microprocessor that was designed by a small team led by Chuck Peddle for MOS Technology.

8-bit microprocessor that was designed by a small team led by Chuck Peddle for MOS Technology.

A MOS Technology 6502 processor in a DIP-40 plastic package. The four-digit date code indicates it was made in the 45th week (November) of 1985.
Motorola 6800 demonstration board built by Chuck Peddle and John Buchanan in 1974
A 1973 MOS Technology advertisement highlighting their custom integrated circuit capabilities
MOS Technology MCS6501, in white ceramic package, made in late August 1975
Introductory advertisement for the MOS Technology MCS6501 and MCS6502 microprocessors
MOS Technology MCS6502, in white ceramic package, manufactured in late 1975
The May 1976 datasheet omitted the 6501 microprocessor that was in the [[:File:MCS650X Datasheet Aug 1975 cover.jpg|August 1975]] version.
6502 processor die. The regular section at the top is the instruction decoding ROM, the seemingly random section in the center is the control logic, and at the bottom are the registers (right) and the ALU (left). The data bus connections are along the lower right, and the address bus along the bottom and lower left.
6502 pin configuration (40-pin DIP)
6502 processor die with drawn in NMOS-transistors and labels hinting at the functionality of the 6502's components
Acorn Atom
Acorn Electron
Apple I
Apple II
Apple IIe
Atari 2600
Atari 5200
Atari 7800
Atari 800
Atari Lynx
BBC Master
BBC Micro
Commodore PET
Commodore VIC-20
Commodore 64
Commodore 128
Family Computer (Famicom)
Nintendo Entertainment System
Ohio Scientific Challenger 4P
Orao
Oric-1
Oric Atmos
Tamagotchi digital pet<ref>{{cite web|url=https://www.kwartzlab.ca/2013/05/code-execution-tamagotchi/|title=Code Execution on a Tamagotchi|date=7 May 2013|website=kwartzlab.ca|access-date=2018-12-23|archive-url=https://web.archive.org/web/20180831185727/https://www.kwartzlab.ca/2013/05/code-execution-tamagotchi/|archive-date=2018-08-31|url-status=dead}}</ref>
TurboGrafx-16
Commodore 64

To start with, one of the two accumulators was removed.

Intel P8051 microcontroller

Intel 8051

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Single chip microcontroller (MCU) series developed by Intel in 1980 for use in embedded systems.

Single chip microcontroller (MCU) series developed by Intel in 1980 for use in embedded systems.

Intel P8051 microcontroller
i8051 microarchitecture
Intel 8031 microcontrollers
Intel D87C51 microcontroller
Silicon Storage Technology 89V54RD2
AMD D87C51
MHS S-80C31
OKI M80C31
Philips PCB80C31
Signetics SCN8031
Temic TS80C32
Atmel AT89C2051
Infineon SAB-C515
Philips S87C654
Siemens SAB-C501
STC Micro STC89C52

8-bit arithmetic logic unit (ALU) and accumulator, 8-bit registers (one 16-bit register with special move instructions), 8-bit data bus and 2×16-bit address buses, program counter, data pointer, and related 8/11/16-bit operations; hence it is mainly an 8-bit microcontroller

IBM 701 operator's console

IBM 701

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IBM’s first commercial scientific computer and its first series production mainframe computer, which was announced to the public on May 21, 1952.

IBM’s first commercial scientific computer and its first series production mainframe computer, which was announced to the public on May 21, 1952.

IBM 701 operator's console
IBM 701 processor frame, showing 1071 of the vacuum tubes
Vacuum tube logic module from a 700 series IBM computer.
Williams tube from an IBM 701 at the Computer History Museum

1) The accumulator was 38 bits long (adding two overflow bits).

PIC microcontrollers in DIP and QFN packages

PIC microcontrollers

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Family of microcontrollers made by Microchip Technology, derived from the PIC1650 originally developed by General Instrument's Microelectronics Division.

Family of microcontrollers made by Microchip Technology, derived from the PIC1650 originally developed by General Instrument's Microelectronics Division.

PIC microcontrollers in DIP and QFN packages
16-bit 28-pin PDIP PIC24 microcontroller next to a metric ruler
Die of a PIC12C508 8-bit, fully static, EEPROM/EPROM/ROM-based CMOS microcontroller manufactured by Microchip Technology using a 1200 nanometre process
Die of a PIC16C505 CMOS ROM-based 8-bit microcontroller manufactured by Microchip Technology using a 1200 nanometre process
Various older (EPROM) PIC microcontrollers
Microchip PIC16C58A
PIC16LF870 in SOIC Socket
This is a 2003 era programmer for the Microchip "PIC" family of microcontrollers. It connects by RS 232 cable to a PC compatible running development software. In 2003 this unit cost $300 Canadian (about $200 US at the time).
1886VE2U

One accumulator (W0), the use of which (as source operand) is implied (i.e. is not encoded in the opcode)

Four ENIAC panels and one of its three function tables, on display at the School of Engineering and Applied Science at the University of Pennsylvania

ENIAC

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The first programmable, electronic, general-purpose digital computer, completed in 1945.

The first programmable, electronic, general-purpose digital computer, completed in 1945.

Four ENIAC panels and one of its three function tables, on display at the School of Engineering and Applied Science at the University of Pennsylvania
Glenn A. Beck (background) and Betty Snyder (foreground) program ENIAC in BRL building 328. (U.S. Army photo, c. 1947–1955)
Cpl. Irwin Goldstein (foreground) sets the switches on one of ENIAC's function tables at the Moore School of Electrical Engineering. (U.S. Army photo)
Programmers Betty Jean Jennings (left) and Fran Bilas (right) operate ENIAC's main control panel at the Moore School of Electrical Engineering. (U.S. Army photo from the archives of the ARL Technical Library)
The bottoms of three accumulators at Fort Sill, Oklahoma, US
A function table from ENIAC on display at Aberdeen Proving Ground museum.
Detail of the back of a section of ENIAC, showing vacuum tubes
ENIAC on a Chip, University of Pennsylvania (1995) - Computer History Museum

ENIAC had 20 ten-digit signed accumulators, which used ten's complement representation and could perform 5,000 simple addition or subtraction operations between any of them and a source (e.g., another accumulator or a constant transmitter) per second.