source: t29-www/en/devices/plated-wire-storage.shtm @ 7

Last change on this file since 7 was 7, checked in by sven, 16 years ago
  • Die Uebersetzung geht weiter: Faxtechnik fertig übersetzt (/en/communication/fax.shtm)
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3<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="de">
4<head><!--#set var="title"        value="Plated wire storage"
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15<div id="extra" class="content">
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18    <div class="box right">
19        <img src="/shared/photos/rechnertechnik/grafiken/magnetdrahtspeicher-uebersicht.en.gif" alt="plated wire storage overview picture, shows the relationship between word straps and plated wires" />
20    </div>
21
22    <p>In the early 1970s, magnetical core memory was quite expensive. The cycle time (time needed to read and rewrite the information) was quite big, because all information had to be rewritten after they had been read.
23      <br/>As a replacement, the plated wire was invented, just before the first semiconductor memories were ready for beeing mass-produced. The plated wire consists of magnetic wire which replaces the cores (see picture at the right).</p>
24
25    <p>The installations from the UNIVAC 9000 series (like our <a href="/en/devices/univac9400/univac_9300.shtm">UNIVAC 9300</a>) were equipped with plated wire storages. We could offer pictures of our storage units, but the assembly of this type of memory is quite opaque. Therefore we publish self-drawn diagrams to illustrate the plated wire characteristics.</p>
26
27    <div class="box center" style="clear:right;">
28        <img src="/shared/photos/rechnertechnik/grafiken/magnetdrahtspeicher-details.en.gif" alt="Detailed diagram: Plated Wire Characteristics, labeled" />
29    </div>
30
31    <p>The plated wire constists of copper with a thin film which consists of an iron-nickel alloy. These plated wires are embedded into word straps which are perpendicular to two sides of the plated wire. In the easy direction of magnetization (see diagram above), the magnet layer is quite stable, whereas it is unstable in the hard direction of magnetization.
32    <br/>To read the information, the word current is raised. The current will establish a magnetic field which tries to align the magnetization vector at the area in the plated wire covered by the word strap.
33    Lengthwise, the magnetic film is very hard to magnetize, therefore the vector only librates (insteads of rotating) <!--and falls back to the former position after the word current was lowered.-->
34    and falls back to the former position. This libration induces a small voltage. The sign of this voltage depends on the direction of the magnetization vector. Therefore it is possible to read a bit without destroying its value. This saves valuable access time, compared to the core memory.</p>
35
36    <div class="box left">
37        <img src="/shared/photos/rechnertechnik/grafiken/magnetdrahtspeicher-lesen.en.gif" alt="Small diagram explaining the read process (pulse on word strap)" />
38    </div>
39    <div class="box right">
40        <img src="/shared/photos/rechnertechnik/grafiken/magnetdrahtspeicher-schreiben.en.gif" alt="Small diagram explaining the write process (pulse on both word strap and plated wire)" />
41    </div>
42
43    <p>To change a bit, its the same procedure, but in addition to the raised word current, there is also a current in the plated wire (bit current). The affecting magnetic field can change the direction of a domain (binary storage cell). Therewith a new information was saved.</p>
44
45    <p style="clear:both;">
46      In principle this was an ingenius idea: No need to thread the cores, fast cycle time, very cheap to produce...
47      <br/>But there is a rub in it. The construction is very sensitive and error-prone. While the wires could be replaced in the former storage systems, typical plated wire storages were completely stuck together so they could not be repared later on. This was a disaster for the companies which made use of this storage.
48      <br/>Fortunately, the first semiconductor memories were mass-produced in the early 1970s, so most of the computers featuring plated wire storage could be upgraded to semiconductor memories made by INTEL.</p>
49
50    <ul id="nav">
51          <li><a href="/en/computer/storage-media.shtm#plated-wire-storage">Storage media</a></li>
52          <li><a href="/en/">technikum29 homepage</a></li>
53    </ul>
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56</body>
57</html>
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