computer architecture In computer engineering, computer architecture is a description of the structure of a computer system made from component parts. It can sometimes be a high-level description that ignores details of the implementation. At a more detailed level, t ...

, 1-bit

integer An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign (−1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the language ...

s or other

data In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted ...

units are those that are (1/8

octet Octet may refer to: Music * Octet (music), ensemble consisting of eight instruments or voices, or composition written for such an ensemble ** String octet, a piece of music written for eight string instruments *** Octet (Mendelssohn), 1825 compos ...

) wide. Also, 1-bit

central processing unit A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, an ...

(CPU) and

arithmetic logic unit In computing, an arithmetic logic unit (ALU) is a Combinational logic, combinational digital circuit that performs arithmetic and bitwise operations on integer binary numbers. This is in contrast to a floating-point unit (FPU), which operates on ...

(ALU) architectures are those that are based on

register Register or registration may refer to: Arts entertainment, and media Music * Register (music), the relative "height" or range of a note, melody, part, instrument, etc. * ''Register'', a 2017 album by Travis Miller * Registration (organ), th ...

s of that size. There are no computers or

microcontroller A microcontroller (MCU for ''microcontroller unit'', often also MC, UC, or μC) is a small computer on a single VLSI integrated circuit (IC) chip. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable i ...

s of any kind that are exclusively 1-bit for all registers and

address bus In computer architecture, a bus (shortened form of the Latin '' omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This e ...

es. A 1-bit register can only store 2¹ different values, i.e. 0 or 1 (off or on, respectively). This is very restrictive and therefore not enough for a

program counter The program counter (PC), commonly called the instruction pointer (IP) in Intel x86 and Itanium microprocessors, and sometimes called the instruction address register (IAR), the instruction counter, or just part of the instruction sequencer, is ...

which, on modern systems, is implemented in an on-chip register, that isn't implemented on-chip in some 1-bit systems.

Opcode In computing, an opcode (abbreviated from operation code, also known as instruction machine code, instruction code, instruction syllable, instruction parcel or opstring) is the portion of a machine language instruction that specifies the operat ...

s for at least one 1-bit processor architecture were 4-bit and the address bus was 8-bit. While 1-bit CPUs are obsolete, the first

carbon nanotube computer Carbon nanotube computers are a class of experimental computing processors constructed from carbon nanotube field-effect transistors, instead of from conventional silicon-based field-effect transistors. __NOTOC__ In a carbon nanotube field-effe ...

from 2013 is a 1-bit

one-instruction set computer A one-instruction set computer (OISC), sometimes called an ultimate reduced instruction set computer (URISC), is an abstract machine that uses only one instructionobviating the need for a machine language opcode. With a judicious choice for the si ...

(and has only 178 transistors).

1-bit

serial computer A serial computer is a computer typified by bit-serial architecture i.e., internally operating on one bit or digit for each clock cycle. Machines with serial main storage devices such as acoustic or magnetostrictive delay lines and rotating ma ...

processes data a single bit at a time. For example, the

PDP-8/S The PDP-8 is a 12-bit minicomputer that was produced by Digital Equipment Corporation (DEC). It was the first commercially successful minicomputer, with over 50,000 units being sold over the model's lifetime. Its basic design follows the pioneeri ...

was a 12-bit computer using a 1-bit ALU, processing the 12 bits serially. An example of a 1-bit computer built from discrete logic SSI chips is the

Wang 500 Wang may refer to: Names * Wang (surname) (王), a common Chinese surname * Wāng (汪), a less common Chinese surname * Titles in Chinese nobility * A title in Korean nobility * A title in Mongolian nobility Places * Wang River in Thailand ...

(1970/1971) calculator as well as the Wang 1200 (1971/1972) word processor series developed by

Wang Laboratories Wang Laboratories was a US computer company founded in 1951 by An Wang and G. Y. Chu. The company was successively headquartered in Cambridge, Massachusetts (1954–1963), Tewksbury, Massachusetts (1963–1976), and finally in Lowell, Massachusett ...

. An example of a 1-bit architecture that was marketed as a CPU is the

Motorola MC14500B The MC14500B Industrial Control Unit (ICU) is a CMOS 1-bit architecture, one-bit microprocessor designed by Motorola for simple control applications in 1977. Overview MC14500B (ICU) is well-suited to the implementation of ladder logic, and ...

Industrial Control Unit (ICU), introduced in 1977 and manufactured at least up into the mid 1990s. Its manual states: One of the computers known to be based on this CPU was the

WDR 1-bit computer The MC14500B Industrial Control Unit (ICU) is a CMOS one-bit microprocessor designed by Motorola for simple control applications in 1977. Overview MC14500B (ICU) is well-suited to the implementation of ladder logic, and thus could be used ...

. A typical sequence of instructions from a program for a 1-bit architecture might be: * load digital input 1 into a 1-bit register; * OR the value in the 1-bit register with input 2, leaving the result in the register; * write the value in the 1-bit register to output 1. This architecture was considered superior for programs making decisions rather than performing arithmetic computations, for

ladder logic Ladder logic was originally a written method to document the design and construction of relay racks as used in manufacturing and process control. Each device in the relay rack would be represented by a symbol on the ladder diagram with connecti ...

as well as for serial data processing. There are also several design studies for 1-bit architectures in academia, and corresponding 1-bit logic can also be found in programming. Other examples of 1-bit architectures are

programmable logic controller A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity tha ...

s (PLCs), programmed in

instruction list Instruction list (IL) is one of the 5 languages supported by the initial versions of IEC 61131-3 standard, and subsequently deprecated in the third edition. It is designed for programmable logic controllers (PLCs). It is a low level language and ...

(IL). Several early

massively parallel Massively parallel is the term for using a large number of computer processors (or separate computers) to simultaneously perform a set of coordinated computations in parallel. GPUs are massively parallel architecture with tens of thousands of t ...

computers used 1-bit architectures for the processors as well. Examples include the May 1983

Goodyear MPP The Goodyear Massively Parallel Processor (MPP) was a massively parallel processing supercomputer built by Goodyear Aerospace for the NASA Goddard Space Flight Center. It was designed to deliver enormous computational power at lower cost than oth ...

and the 1985

Connection Machine A Connection Machine (CM) is a member of a series of massively parallel supercomputers that grew out of doctoral research on alternatives to the traditional von Neumann architecture of computers by Danny Hillis at Massachusetts Institute of Techno ...

. By using a 1-bit architecture for the individual processors a very large array (e.g. the Connection Machine had 65,536 processors) could be constructed with the chip technology available at the time. In this case the slow computation of a 1-bit processor was traded off against the large number of processors. 1-bit CPUs can now be considered obsolete; not many kinds have ever been produced, still some MC14500B chips are available from brokers for obsolete parts.

References

External links

* {{CPU technologies Data unit Programmable logic controllers

1-bit

See also

References

Further reading

External links