Editing Hybrid computer

{{Short description|Combination of analog and digital computer}}
{{about|analog-digital hybrid computers|laptop-tablet computers|2-in-1 PC}}
{{More citations needed|date=March 2022}}
[[File:WAT 1001.jpg|thumb|300px|Polish hybrid computer [[WAT 1001]]]]
'''Hybrid computers''' are computers that exhibit features of [[analog computer]]s and [[digital computer]]s. The digital component normally serves as the controller and provides [[logic]]al and [[numerical analysis|numerical]] operations, while the analog component often serves as a solver of [[differential equations]] and other mathematically complex problems.{{Citation needed|date=February 2025}}

==History==
The first desktop hybrid computing system was the Hycomp 250, released by Packard Bell in 1961.<ref>{{cite web|title=HYCOMP"250-THE FIRST DESK TOP HYBRlD ANALOG/Digital COMPUTING SYSTEM|url=http://archive.computerhistory.org/resources/text/Packard_Bell/PackardBell.HYCOMP250.1961.102646194.pdf}}</ref> Another early example was the HYDAC 2400, an integrated hybrid computer released by [[Electronic Associates|EAI]] in 1963.<ref>{{cite web|title=HYDAC 2400 Hybrid Digital/Analog Computer|url=http://archive.computerhistory.org/resources/text/EAI/EAI.HYDAC2400.1963.102646295.pdf}}</ref> In the 1980s,  Marconi Space and Defense Systems Limited (under [[Peggy Hodges]]) developed their "Starglow Hybrid Computer", which consisted of three EAI 8812 analog computers linked to an EAI 8100 digital computer, the latter also being linked to an SEL 3200 digital computer.<ref>{{Cite book|url=https://www.sto.nato.int/publications/AGARD/AGARD-AG.../AGARD-AG-279.pdf|title=AGARDograph No. 279 Survey of Missile Simulation and Flight Mechanics Facilities in NATO.|publisher=NATO|year=1983}}{{Dead link|date=June 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Late in the 20th century, hybrids dwindled with the increasing capabilities of digital computers including [[digital signal processor]]s.<ref>[https://books.google.com/books?id=71ayYLt_1MkC&dq=hybrid+computers+obsolete&pg=PA265 The Analogue Alternative], the Electronic Analog Computer in Britain and the USA, 1930-1975, by James S Small</ref>

In general, [[analog computer]]s are extraordinarily fast, since they are able to solve most mathematically complex equations at the rate at which a signal traverses the circuit, which is generally an appreciable fraction of the speed of light.  On the other hand, the [[precision (computer science)|precision]] of analog computers is not good; they are limited to three, or at most, four digits of precision.{{Citation needed|date=February 2025}}

[[Digital computer]]s can be built to take the solution of equations to almost unlimited precision, but quite slowly compared to analog computers.  Generally, complex mathematical equations are approximated using [[iterative method]]s which take huge numbers of iterations, depending on how good the initial "guess" at the final value is and how much precision is desired.  (This initial guess is known as the numerical "seed".)  For many [[real-time computing|real-time]] operations in the 20th century, such ''digital'' calculations were too slow to be of much use (e.g., for very high frequency [[phased array radar]]s or for weather calculations), but the precision of an ''analog'' computer is insufficient.{{Citation needed|date=February 2025}}

Hybrid computers can be used to obtain a very good but relatively [[accuracy and precision|imprecise]] 'seed' value, using an analog computer front-end, which is then fed into a digital computer iterative process to achieve the final desired degree of precision.  With a three or four digit, highly accurate numerical seed, the total digital computation time to reach the [[significant figures|desired precision]] is dramatically reduced, since many fewer iterations are required.  One of the main technical problems to be overcome in hybrid computers is minimizing digital-computer [[noise (electronics)|noise]] in analog computing elements and grounding systems.{{Citation needed|date=February 2025}}

Consider that the [[nervous system]] in animals is a form of hybrid computer.  Signals pass across the [[synapses]] from one [[nerve cell]] to the next as discrete (digital) packets of chemicals, which are then summed within the nerve cell in an analog fashion by building an electro-chemical potential until its [[Threshold potential|threshold]] is reached, whereupon it discharges and sends out a series of digital packets to the next nerve cell. The advantages are at least threefold: noise within the system is minimized (and tends not to be additive), no common grounding system is required, and there is minimal degradation of the signal even if there are substantial differences in activity of the cells along a path (only the signal delays tend to vary).  The individual nerve cells are analogous to analog computers; the synapses are analogous to digital computers.{{Citation needed|date=February 2025}}

Hybrid computers are distinct from [[hybrid systems]].  The latter may be no more than a digital computer equipped with an [[analog-to-digital converter]] at the input and/or a [[digital-to-analog converter]] at the output, to convert analog signals for ordinary digital signal processing, ''and conversely'', e.g., for driving physical control systems, such as [[servomechanism]]s.{{Citation needed|date=February 2025}}

== VLSI hybrid computer chip ==
In 2015, researchers at Columbia University published a paper<ref>{{Cite book|date = 2015-09-01|pages = 279–282|doi = 10.1109/ESSCIRC.2015.7313881|first1 = Ning|last1 = Guo|first2 = Yipeng|last2 = Huang|first3 = Tao|last3 = Mai|first4 = S.|last4 = Patil|first5 = Chi|last5 = Cao|first6 = Mingoo|last6 = Seok|first7 = S.|last7 = Sethumadhavan|first8 = Y.|last8 = Tsividis| title=ESSCIRC Conference 2015 - 41st European Solid-State Circuits Conference (ESSCIRC) | chapter=Continuous-time hybrid computation with programmable nonlinearities |isbn = 978-1-4673-7470-5| s2cid=16523767 }}</ref> on a small scale hybrid computer in 65&nbsp;nm CMOS technology. This 4th-order VLSI hybrid computer contains 4 integrator blocks, 8 multiplier/gain-setting blocks, 8 fanout blocks for distributing current-mode signals, 2 ADCs, 2 DACs and 2 SRAMs blocks. Digital controllers are also implemented on the chip for executing the external instructions. A robot experiment in the paper demonstrates the use of the hybrid computing chip in today's emerging low-power embedded applications.{{Citation needed|date=February 2025}}

==References==
{{reflist}}

== External links ==
* [http://digicoll.library.wisc.edu/cgi-bin/UW/UW-idx?type=div&did=UW.WIEv105no2.DGreco&isize=M A New Tool For Science] By Daniel Greco and Ken Kuehl, The Wisconsin Engineer, Nov 1972, reprinted Feb 2001
* {{cite journal |vauthors=Nadel LD, Kramer MR, Shultheis DC, McCulloh TA |title=A hybrid computer system for use in cardiology |journal=Med Prog Technol |volume=4 |issue=4 |pages=185–91 |date=April 1977 |pmid=865418}}
*{{cite journal|title=HYBRID COMPUTATION: WHAT AND WHY?|journal=Computers and Automation|date=Oct 1963|volume=XII|issue=10|pages=[https://archive.org/details/bitsavers_computersA_6121266/page/n9 10]–17|url=https://archive.org/details/bitsavers_computersA_6121266}}

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[[Category:Computing terminology]]
[[Category:Classes of computers]]
[[Category:Analog computers]]