Content deleted Content added
m Reverted edits by 171.253.139.193 (talk) (HG) (3.4.11) |
Thumperward (talk | contribs) split off a lead. rm a paragraph sourced to a bleeding ebay search results list |
||
Line 3:
{{Computer architecture bit widths}}
In [[computer architecture]], '''4-bit''' [[Integer (computer science)|integer]]s, or other [[data (computer science)|data]] units are those that are 4 [[bit]]s wide. Also, 4-bit [[central processing unit]] (CPU) and [[arithmetic logic unit]] (ALU) architectures are those that are based on [[processor register|register]]s, or [[Bus (computing)|data bus]]es of that size. [[Memory address]]es (and thus [[address bus]]es) for 4-bit CPUs are generally much larger than 4-bit (since only 16 memory locations would be very restrictive), such as 12-bit or more, while they could in theory be 8-bit. A group of four bits is also called a [[nibble]] and has 2<sup>4</sup> = 16 possible values.
== History ==
Some of the first [[microprocessor]]s had a 4-bit word length and were developed around 1970. Traditional (non-quantum) 4-bit computers are by now obsolete, while recent [[quantum computer]]s are 4-bit,<ref>{{Cite web|title=Qiskit/openqasm|url=https://github.com/Qiskit/openqasm|access-date=2020-11-16|quote=bigadder.qasm: Quantum ripple-carry adder. 8-bit adder made out of 2 4-bit adders from adder.qasm.|website=GitHub|language=en}}</ref><ref>{{cite arXiv|last1=Cross|first1=Andrew W.|last2=Bishop|first2=Lev S.|last3=Smolin|first3=John A.|last4=Gambetta|first4=Jay M.|date=2017-07-13|title=Open Quantum Assembly Language|class=quant-ph|quote=The only storage types of Open QASM (version 2.0) are classical and quantum registers, which are one-dimensional arrays of bits and qubits, respectively.|eprint=1707.03429}}</ref> but also based on [[qubit]]s, such as the [[IBM Q Experience]]. See also: [[Bit slicing#Bit-sliced quantum computers]].
Line 34 ⟶ 36:
The [[HP Saturn]] processors, used in many [[Hewlett-Packard]] calculators between 1984<!-- intro of HP-71B --> and 2003<!-- when the HP49 was discontinued and replaced by an ARM based model developed by Kinpo --> <!-- EOL announcement of HP 50g --> (including the [[HP 48 series]] of scientific calculators) are "4-bit" (or hybrid 64-/4-bit) machines; as the Intel 4004 did, they string multiple 4-bit words together, e.g. to form a 20-bit memory address, and most of the registers are 64 bits wide, storing 16 4-bit digits.<!-- Its instructions were 10 bits wide.--><!-- The previous statement is factually inaccurate and not supported by the cited sources --><!-- <ref name="HPM">{{cite web |url=http://www.hpmuseum.org/techcpu.htm |title=HP CPU and Programming |access-date=2014-01-14}}</ref> --><!-- This reference is invalid because it points to a page which describes the microarchitectures of the HP41 and older calculators which did not use the Saturn. The reference has been updated to point to the H.P. Saturn specific page. --><ref name="HPM_Saturn"/><ref name="Grack_Saturn"/><ref name="HPCalc_Saturn"/><!--{{Off-topic|date=December 2015|HP Saturn}}Since 2003, new Saturn-based HP calculators{{Dubious |date=December 2015| reason=These are not "Saturn-based" processors. The "Saturn+" isn't even a Saturn processor, but an emulation of one.}} (including the [[HP 49/50 series]]) use a 32-bit processor with an [[ARM920T]] core to emulate an extended Saturn processor architecture named [[HP Saturn+|Saturn+]] at a higher speed. -->
In addition, some early calculators{{snd}} such as the 1967 [[Casio AL-1000]], the 1972 [[Sinclair Executive]], and the aforementioned 1984 [[HP Saturn]]{{snd}} had 4-bit [[datapath]]s that accessed their registers 4 bits (one BCD digit) at a time.<ref>[http://www.vintagecalculators.com/html/casio_al-1000.html "Desk Electronic Calculators: Casio AL-1000"]</ref>
==Uses==
| |||