1-bit computing

In computer architecture, 1-bit integers, memory addresses, or other data units are those that are 1 bit (1/8 octet) wide. Also, 1-bit CPU and ALU architectures are those that are based on registers, address buses, or data buses of that size.

Not to be confused with bit or one instruction set computer.
"1-bit" redirects here. For the oversampling digital-to-analog converter technology, see 1-bit DAC. For 1-bit images where each pixel is stored as a single bit, see binary image.
Computer architecture bit widths
Bit
Application
Binary floating-point precision
  • 16
  • 32
  • 40
  • 64
  • 80
  • 128
  • 256
Decimal floating-point precision
1-bit microprocessor MC14500BCP

A serial computer processes data a single bit at a time. For example, the PDP-8/S was a 12-bit computer using a 1-bit ALU, processing the 12 bits serially.[1]

An example of a 1-bit computer built from discrete logic SSI chips is the Wang 500 (1970/1971) calculator[2][3] as well as the Wang 1200 (1971/1972)[4] 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),[5][6] introduced in 1977 and manufactured at least up into the mid 1990s.[6] One of the computers known to be based on this CPU was the WDR 1-bit computer.[7] 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.[5]

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 now be considered obsolete; not many kinds have ever been produced, still as of 2020 many MC14500B chips are available from brokers for obsolete parts.[8][9]

See also

References
  1. PDP-8/S Maintenance Manual (PDF). Digital Equipment Corporation. August 1969. p. 3–14.
  2. Wasserman, Katie (March 2006) [January 2004]. "LED calculators rule her house". Computer Collector Newsletter / Technology Rewind (Interview). Interviewed by Koblentz, Evan. Archived from the original on 2019-12-27. 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.
  3. 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.
  4. Battle, Jim (2010-03-07). "Wang 1200 - Wang WP History". Archived from the original on 2017-05-21. Retrieved 2017-05-21.
  5. 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".)
  6. 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.
  7. Ludwig, Volker; Paschenda, Klaus; Schepers, Heinz; Terglane, Hermann-Josef; Grannemann, Klaus; John, Burkhard; Komar, Hermann; Meinersen, Ludwig (1986). Fast alles über den WDR-1-Bit-Computer (PDF) (in German). Neuss & Recklinghausen, Germany: DATANorf. Archived (PDF) from the original on 2017-05-20. Retrieved 2017-05-20.
  8. "MC14500B Price & Stock". www.digipart.com. Retrieved 2019-11-04.
  9. "MC14500B". www.ebay.com. Retrieved 2019-11-04.

Further reading
  • 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.


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