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)

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Processor register

Quickly accessible location available to a computer's processor.

Transistor count over time, demonstrating Moore's law

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.

MOS Technology 6502

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

ENIAC

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.

Intel 8080

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).

PDP-8

12-bit minicomputer that was produced by Digital Equipment Corporation .

A PDP-8 on display at The National Museum of Computing in Bletchley, England. This example is from the first generation of PDP-8s, built with discrete transistors and later known as the Straight 8.
A PDP-8 on display at The National Museum of Computing in Bletchley, England. This example is from the first generation of PDP-8s, built with discrete transistors and later known as the Straight 8.
An open PDP-8/E with its logic modules behind the front panel and one dual TU56 DECtape drive at the top
A "Straight-8" running at the Stuttgart Computer Museum
PDP-8/e at the Living Computers Museum.
PDP-8/I core memory stack
One of three inter-connected modules that make up a PDP-8 core memory plane.
One of three inter-connected modules that make up a PDP-8 core memory plane. This is the middle of the three and contains the array of actual ferrite cores.
One of three inter-connected modules that make up a PDP-8 core memory plane.

It also has only three programmer-visible registers: A 12-bit accumulator (AC), a program counter (PC), and a carry flag called the "link register" (L).

Instruction set architecture

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):, ,.

Intel 8051

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

Intel 4004

4-bit central processing unit released by Intel Corporation in 1971.

White ceramic Intel C4004 microprocessor with grey traces
The Unicom 141P is an OEM version of the Busicom 141-PF.
National Semiconductor was a second-source manufacturer of the 4004, under their part number INS4004.
Two C4004 DIPs, with one opened to show the die
Intel 4004 architectural block diagram
Intel 4004 DIP chip pinout
In the lower-right corner of the CPU are the initials "F.F."
The ceramic C4004 variant without grey traces
The ceramic D4004 variant
The plastic P4004 variant

He also modified the Branch Back (return from subroutine) instruction to clear the accumulator.

IBM 650

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.

Data General Nova

Series of 16-bit minicomputers released by the American company Data General.

A Nova system (beige and yellow, center bottom) and a cartridge hard disk system (opened, below Nova) in a mostly empty rack mount.
Data General Nova 1200 front panel
A Nova 1200, mid-right, processed the images generated by the EMI-Scanner, the world's first commercially available CT scanner.
Nova 1200 CPU printed circuit board. The 74181 ALU is the large IC center-right.
Running Nova 840 (The front panel has been replaced with one from a 1220)
Data General Nova 3
Data General mN601 microprocessor
Data General software on punched tape

As the complexity of a flip-flop was being rapidly reduced as they were implemented in chips, the design offset the lack of addressing modes of the load/store design by adding four general-purpose accumulators, instead of the single register that would be found in similar low-cost offerings like the PDP series.