1-bit architecture

A 1-bit computer architecture is an instruction set architecture for a processor that has datapath widths and data register widths of 1 bit (1/8 octet) wide.

An example of a 1-bit computer built from discrete logic SSI chips[1][2] were the Wang 700 (1968/1970)[3] and Wang 500 (1970/1971)[4] calculator as well as the Wang 1200 (1971/1972)[5] word processor series of Wang Laboratories.

An example of a 1-bit architecture that was marketed as a CPU is the Motorola MC14500B Industrial Control Unit (ICU),[6][7] introduced in 1977 and manufactured at least up into the mid 1990s.[7] One of the computers known to be based on this CPU was the WDR 1-bit computer.[8] 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 as well as for serial data processing.[6]

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 controllers (PLCs), programmed in instruction list (IL).

Several early massively parallel computers used 1-bit architectures for the processors as well. Examples include the Goodyear MPP and the Connection Machine. 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 meanwhile be considered obsolete, not many kinds have been produced and none are known to be available in the major computer component stores (as of 2019, a few MC14500B chips are still available from brokers for obsolete parts.[9][10]).

1-bit microprocessor MC14500BCP

See also


  1. ^ Wasserman, Katie (March 2006) [January 2004]. "LED calculators rule her house". Computer Collector Newsletter / Technology Rewind (Interview). Interviewed by Koblentz, Evan. Retrieved 2017-05-20. Probably my most favorite is the Wang 500. It's got several unique things about it: a very unusual ROM memory made of hundreds of long enamel-coated wires wrapped around iron cores; a super-fast single-bit CPU built out of SSI logic chips; and of course tons of really cool-looking colorful keys.
  2. ^ Product Service - Schematic manual (PDF). Wang Laboratories, Inc. 1974. 03-0019-0. Archived (PDF) from the original on 2017-05-20. Retrieved 2017-05-20.
  3. ^ Müller, H. "Programmierbare Rechner der 3. Generation mit einfacher IC-Technik" (in German). Kelkheim/Taunus, Germany: technikum29. Wang 700 & Wang 500. Archived from the original on 2017-05-20. Retrieved 2017-05-20.
  4. ^ "Wang Model 500 programmable calculator". Computer History Museum (CHM). Catalog Number X222.83. Archived from the original on 2017-05-20. Retrieved 2017-05-20.
  5. ^ Battle, Jim (2010-03-07). "Wang 1200 - Wang WP History". Archived from the original on 2017-05-21. Retrieved 2017-05-21.
  6. ^ a b Gregory, Vern; Dellande, Brian; DiSilvestro, Ray; Malarkey, Terry; Smith, Phil; Hadley, Mike (1977). Motorola MC14500B Industrial Control Unit Handbook - Theory and Operation of a CMOS one-bit processor compatible with B series CMOS devices (PDF). Motorola Semiconductor Products Inc. 33-B78/8.0. Retrieved 2017-05-20. (NB. Also available in German language under the title "Motorola MC14500B Industrial Control Unit Handbuch - Theorie und Anwendung eines Ein-Bit-CMOS-Prozessors".)
  7. ^ a b Industrial Control Unit MC14500B (PDF). Motorola CMOS Logic Data. Semiconductor Technical Data (revision 3 ed.). Motorola. 1995. pp. 306–313. Archived (PDF) from the original on 2017-05-20. Retrieved 2012-08-01.
  8. ^ Ludwig, Volker; Paschenda, Klaus; Schepers, Heinz; Terglane, Hermann-Josef; Grannemann, Klaus; John, Burkhard; Komar, Hermann; Meinersen, Ludwig (1986). Written at Neuss & Recklinghausen, Germany. Fast alles über den WDR-1-Bit-Computer (PDF) (in German). Neuss, Germany: DATANorf. Archived (PDF) from the original on 2017-05-20. Retrieved 2017-05-20.
  9. ^ "Motorola IC MC14500B / MC14500BCL (100% NEW)". eBay. Retrieved 2019-01-15., "5PCS MC14500BCP Encapsulation:DIP-16,Industrial Control Unit". eBay. Retrieved 2019-01-15.
  10. ^ "CMOS-LOGIC IC 4500 DIP16". Archived from the original on 2017-05-20. Retrieved 2017-01-03. Also known as MC14500BCP

Further reading

External links

  • Schembri, Thierry; Bizoirre, Sylvain; Boisseau, Olivier; Chauvaud, Pierre-Emmanuel. "WDR-1-Bit Computer". OLD-COMPUTERS.COM. Archived from the original on 2017-05-20. Retrieved 2017-05-20.
Bit-serial architecture

In digital logic applications, bit-serial architectures send data one bit at a time, along a single wire, in contrast to bit-parallel word architectures, in which data values are sent all bits or a word at once along a group of wires.

All computers before 1951, and most of the early massive parallel processing machines used a bit-serial architecture—they were serial computers.

Bit-serial architectures were developed for digital signal processing in the 1960s through 1980s, including efficient structures for bit-serial multiplication and accumulation.Often N serial processors will take less FPGA area and have a higher total performance than a single N-bit parallel processor.

Instruction list

Instruction List (IL) is one of the 5 languages supported by the IEC 61131-3 standard. It is designed for programmable logic controllers (PLCs). It is a low level language and resembles assembly. All of the languages share IEC61131 Common Elements. The variables and function call are defined by the common elements so different languages can be used in the same program.

Program control (control flow) is achieved by jump instructions and function calls (subroutines with optional parameters).

The file format has now been standardized to XML by PLCopen.

Motorola MC14500B

The MC14500B Industrial Control Unit (ICU) is a CMOS one-bit microprocessor designed by Motorola for simple control applications in 1977. It is well-suited to the implementation of ladder logic, and thus could be used to replace relay systems and programmable logic controllers, also intended for serial data manipulation. The processor supports 16 commands, operating at a frequency of 1 MHz. The MC14500B unit does not include a program counter (PC); instead, a clock signal drives a separate PC chip; therefore the size of supported memory is dependent on the implementation of that chip. It was still in production in 1995.The ICU was conceived by Vern Gregory in the mid-1970s while working as an engineer in a Marketing / Applications group of Motorola Semiconductor Products Sector in Phoenix, AZ; Brian Dellande originated circuit and sub-routine designs, and co-wrote the Manual; Ray DiSilvestro was the bench technician; Terry Malarkey provided management support.

In the CMOS Logic Division in Austin, TX (where it was made) Phil Smith was the chip designer; Mike Hadley provided Product Applications support.

The ICU was a steady seller for 20+ years. As of 2019, at least this 1-bit architecture chip is still available on the aftermarket (on eBay).

A form of the design served as an embedded controller in a custom automotive chip made for NipponDenso by Motorola—Japan.

One of the computers known to be based on this processor is the educational WDR 1-bit computer (512 bits of RAM, LED, I/O, keyboard).The ICU architecture is similar to that of the DEC PDP-14 computer.

Programmable logic controller

A programmable logic controller (PLC) or programmable controller is an industrial digital computer which has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, or robotic devices, or any activity that requires high reliability control and ease of programming and process fault diagnosis.

PLCs were first developed in the automobile manufacturing industry to provide flexible, ruggedized and easily programmable controllers to replace hard-wired relays, timers and sequencers. Since then, they have been widely adopted as high-reliability automation controllers suitable for harsh environments. A PLC is an example of a "hard" real-time system since output results must be produced in response to input conditions within a limited time, otherwise unintended operation will result.

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 magnetic devices were usually serial computers.

Serial computers required much less hardware than their parallel computing counterpart, but were much slower.

Instruction set
Word size
Core count

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