1 | <?php |
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2 | $seiten_id = 'lgp30'; |
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3 | $version = '$Id: elektro-mechanik.php 688 2014-11-15 09:18:06Z heribert $'; |
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4 | $titel = 'Schoppe & Faeser: LGP 30'; |
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5 | |
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6 | require "../../lib/technikum29.php"; |
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7 | ?> |
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8 | |
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9 | <h2 id="lgp30">LGP 30</h2> |
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10 | |
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11 | The 1st-generation dataprocessing system LGP-30 was developed in the United |
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12 | States by <b>L</b>ibrascope and <b>G</b>eneral-<b>P</b>recision in the mid-1950s. About 40 such |
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13 | machines were built under a license agreement by Schoppe & Faeser in Germany. |
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14 | The LGP-30 was intended as a scientific computer system and was superseded |
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15 | by the <a class="go" href="/en/computer/early-computers.php"> <b>LGP-21</b></a> in 1962.<br> |
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16 | |
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17 | Programs and data are stored on 1" paper tape which are fed to a high-speed |
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18 | punch/reader. Manual input and output is performed by a so-called |
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19 | "Flexowriter" made by Friden. This device is basically an electric |
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20 | typewriter with a paper tape attachment.</p><br> |
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21 | |
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22 | <div class="center"> |
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23 | <img src="/shared/photos/rechnertechnik/lgp30-1.jpg" alt="LGP 30" width="850" height="380" /> |
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24 | <p class="center"> |
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25 | <b>LGP-30 vacuum tube based computer - prior to restauration</b> |
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26 | </p></div> |
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27 | |
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28 | <p>Unfortunately, our machine is missing the special interconnect cables |
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29 | for the high-speed paper tape system and the Flexowriter. Therefore we |
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30 | are looking desperately for the required <a class="go" href="/en/wanted.php#connector" target="_blank">special connectors </a>. <br> |
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31 | Apart from this, the machine is in rather good shape. First |
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32 | of all the side panels have to be repainted and all the mechanic parts |
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33 | have to be brought back to working condition. After that the electronics |
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34 | can be debugged - a true adventure, digging deep into vacuum tube based |
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35 | digital electronics.</p> |
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36 | |
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37 | |
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38 | <div style="width: 350px;" class="desc-left borderless no-copyright"> |
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39 | <a class="popup" href="/shared/photos/rechnertechnik/lgp30-2.jpg"> |
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40 | <img src="/shared/photos/rechnertechnik/lgp30-2.jpg" alt="Front View" height="266" width="350"></a> |
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41 | <div class="bildtext"> |
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42 | <p><b>Front View without casing</b></p> <a class="popup" href="/shared/photos/rechnertechnik/lgp30-2.jpg"> enlarge picture</a> |
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43 | </div></div> |
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44 | |
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45 | <div style="width: 350px;" class="desc-right borderless no-copyright"> |
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46 | <a class="popup" href="/shared/photos/rechnertechnik/lgp30-3.jpg"> |
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47 | <img src="/shared/photos/rechnertechnik/lgp30-3.jpg" alt="Backside" height="262" width="350"></a> |
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48 | <div class="bildtext"> |
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49 | <p><b>Backside without casing</b></p> <a class="popup" href="/shared/photos/rechnertechnik/lgp30-3.jpg"> enlarge picture</a> |
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50 | </div></div> |
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51 | |
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52 | <p class="clear">The technical data is rather interesting: The magnetic drum rotates at |
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53 | 3600 RPM, the distance between two adjacent tracks is 2mm, a single track |
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54 | has a width of 1mm and the spacing between read/write heads and the |
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55 | drum surface is 25 um! The memory capacity is pretty large for its time |
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56 | at 4,096 words of 32 bits each. The basic clock frequency is 120 kHz and |
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57 | the access time is between 2 ms and 15 ms. A single addition takes |
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58 | 0.23 ms while a multiplication requires 15 ms (without the necessary |
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59 | access times to the drum).<br> |
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60 | All in all, there are 113 long-life vacuum tubes and 1450 Germanium |
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61 | diodes packaged in 34 modules (12 different module types). <br> |
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62 | Peripherals: |
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63 | The paper tape reads is capable of reading 200 characters/s, the high-speed |
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64 | punch can punch at 50 characters/s while the Flexowriter is capable of |
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65 | printing 10 characters/s. <br> |
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66 | |
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67 | The processing unit (without peripherals) weights 350 kg.</p> |
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68 | |
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69 | |
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70 | <p class="clear">Some historical data regarding our machine: Its whereabouts prior to 1962 |
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71 | are unknown. It was then used from 1962 until 1980 at a land surveying |
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72 | office for various purposes including the generation of control paper |
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73 | tapes for a ZUSE Graphomat Z64 plotter, recalculation of historic |
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74 | triangulation nets, affine transformations, Helmert-transformations, |
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75 | basic tasks for land surveying etc.<br> |
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76 | |
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77 | Those tasks were quite demanding and even a rather simple fit through |
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78 | three points determined by triangulation took about 3 to 4 minutes of |
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79 | computer time.<br><br> |
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80 | |
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81 | |
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82 | <div class="desc-right borderless"> |
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83 | <a href="/shared/photos/rechnertechnik/lgp-trommelspeicher.jpg" target="_blank"> |
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84 | <img src="/shared/photos/rechnertechnik/lgp-trommelspeicher.jpg" alt="Trommelspeicher" height="325" width="420"></a> |
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85 | <div class="bildtext"> |
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86 | <p>LGP-30 Magnetic Drum. The magnetic layer has some defects. <br> The photo can be enlarge.</p> |
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87 | </div> </div> |
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88 | |
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89 | <div id="trommel"></div> |
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90 | |
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91 | <p>Now the restoration of this vaccum tube based computer started. The biggest |
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92 | problem is the magnetic drum memory. Currently four options are under |
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93 | consideration:<br> |
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94 | |
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95 | 1. Applying a new magnetic coating to the damaged drum. This approach would |
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96 | be ideal but also the most complex solution.<br> |
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97 | |
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98 | 2. Simulating the complete drum assembly by a modern microcontroller. |
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99 | Attaching this to the vacuum tube electronics would be feasible by means of |
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100 | level shifters (0V and -20V are required for operation).<br> |
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101 | |
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102 | 3. A discrete approach emplying RAMs, EPROMs, operational amplifiers and lots |
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103 | of glue logic. This does not have any advantages over approach 2.<br> |
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104 | |
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105 | 4. Replacing the rotating drum by a fixed assembly holding magnetic |
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106 | read/write heads, one for each head of the drum. This approach has been |
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107 | abandoned due to its complexity.<br><br> |
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108 | |
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109 | Compared with the complexity of emulating the drum assembly, the missing |
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110 | cables are only a minor problem. Fortunately four experts will support the |
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111 | restoration effort. We would especially like to thank Mr. Klemens Krause |
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112 | <a href="http://computermuseum.informatik.uni-stuttgart.de/"target="_blank">Computermuseum-Stuttgart</a>. |
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113 | |
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114 | |
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