1-bit computing: Difference between revisions

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{{Use list-defined references|date=June 2022}}

{{Computer architecture bit widths}}

[[File:MC14500BCP.jpg|thumb|1-bit [[programmable logic controller]] [[Motorola MC14500B|MC14500BCP]]]]

In [[computer architecture]], '''1-bit''' [[integer (computer science)|integer]]s or other [[Data (computing)|data]] units are those that are {{nowrap|1 [[bit]]}} (1/8 [[octet (computing)|octet]]) wide. Also, 1-bit [[central processing unit]] (CPU) and [[arithmetic logic unit]] (ALU) architectures are those that are based on [[processor register|register]]s of that size.

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There are no computers or [[microcontroller]]s of any kind that are exclusively 1-bit for all registers and [[address bus]]es. A 1-bit register can only store two different values. This is very restrictive and therefore not enough for a [[program counter]] which, on modern systems, is implemented in an on-chip register, but is not implemented on-chip in some 1-bit systems. [[Opcode]]s for at least one 1-bit processor architecture were 4-bit and the address bus was 8-bit.

While 1-bit computing is mostly obsolete, 1-bit [[serial communication]] is still used in modern computers, that are otherwise e.g. 64-bit, and thus also have much larger buses.

While 1-bit CPUs are obsolete, the first (research) [[carbon nanotube computer]] from 2013 is a 1-bit [[one-instruction set computer]] (and has only 178 transistors; since it has only one instruction<!-- SUBNEG (subtract and branch if negative) --> though it can emulate 20 [[MIPS architecture|MIPS]] instructions).<ref name="Courtland_2013"/>

== 1-bit ==

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Other examples of 1-bit architectures are [[programmable logic controller]]s (PLCs), programmed in [[instruction list]] (IL).

Such as the 1969 [[PDP-14]].<ref name=CHD>

{{cite web |url=http://www.chdickman.com/pdp14 |title=DEC PDP-14 Industrial Controller}}

</ref>

Several early [[massively parallel]] computers used 1-bit architectures for the processors as well. Examples include the May 1983 [[Goodyear MPP]] and the 1985 [[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.

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== References ==

{{reflist|refs=

<ref name="Courtland_2013">{{cite web |title=First Computer Made From Carbon Nanotubes Debuts - The modest 1-bit, 1 kHz machine could usher in a new post-silicon era |author-first=Rachel |author-last=Courtland |date=2013-09-25 |website=IEEE Spectrum: Technology, Engineering, and Science News |url=https://spectrum.ieee.org/tech-talk/semiconductors/devices/first-computer-made-from-carbon-nanotubes-debuts |access-date=2021-04-18 |url-status=live |archive-url=https://web.archive.org/web/20220615190932/https://spectrum.ieee.org/first-computer-made-from-carbon-nanotubes-debuts |archive-date=2022-06-15}}</ref>

<ref name="DEC_1969">{{cite book |title=PDP-8/S Maintenance Manual |chapter=III. System Logic - 3.4. Control Circuits - 3.4.1 Adder |date=August 1969 |orig-date=October 1967 |edition=4th printing |publisher=[[Digital Equipment Corporation]] |___location=Maynard, Massachusetts, US |id=F-87S |pages=3-14–3-15 |url=http://www.bitsavers.org/pdf/dec/pdp8/pdp8s/PDP8S_MaintMan.pdf |access-date=2022-06-15 |url-status=live |archive-url=https://web.archive.org/web/20211023025507/http://www.bitsavers.org/pdf/dec/pdp8/pdp8s/PDP8S_MaintMan.pdf |archive-date=2021-10-23}} (191 pages)</ref>

<ref name="Koblentz_2004">{{cite interview |title=LED calculators rule her house |interviewer-first=Evan |interviewer-last=Koblentz |author-first=Katie<!-- aka Kathie / Katherine / Ken --> |author-last=Wasserman |author-link=Ken Wasserman |journal=Computer Collector Newsletter / Technology Rewind |orig-date=January 2004 |date=March 2006 |url=http://www.snarc.net/tr/katie-led.htm |access-date=2017-05-20 |url-status=live |archive-url=https://archive.today/20191227180243/http://www.snarc.net/tr/katie-led.htm |archive-date=2019-12-27 |quote=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.}}</ref>