Changeset 247 in t29-www for en/computer/early-computers.shtm


Ignore:
Timestamp:
Apr 22, 2012, 2:06:43 AM (7 years ago)
Author:
heribert
Message:

Diverse Aenderungen an der ganzen Homepage der letzten Monate,
die halt alle so durch Heribert abliefen.

File:
1 edited

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  • en/computer/early-computers.shtm

    r246 r247  
    3434    </div>
    3535               
    36                 <p>The <b>LPG21</b> computer by General Precision was released and licensed in the
    37 USA in 1962. Paying royalities, the german company "Schoppe & Faser"
    38 copied this computer with a new frontend design, calling it <b>"EUROCOMP"</b>
    39 (1964).<br>
    40  It's a very small mainframe, advertised as the "first
    41 full-capability computer priced from $ 16,250". Of course this price was
    42 only offered for the bare CPU. Including the minimal equipment
    43 (flexowriter, tape reader and puncher) the overall price was about $ 30,000.<br>
     36                <p>This machine is particularly interesting in more than one way: 1) The hardware
     37is extremely simple, 2) the machine already employs a bus system for
     38interconnecting the various units. 3) The machine features a fixed disk which
     39holds all registers as well as timing tracks. As the picture above shows we
     40have two complete systems which simplifies troubleshooting and repair.<br>
     41
     42Citing from the original brochure (1964): "The LGP-21 is produced by Schoppe &
     43Faeser as a licensee in Europe and is distributed by EUROCOMP GmbH."<br>
     44
     45The LGP-21 had been developed by Librascope, division GP1 (USA). This company
     46once was one of the largest calculating machine manufacturers in the world.
     47Starting in 1962 the LGP-21 was marketed in the USA by General Precision. The
     48machine is a very small computer but was advertised as "The first complete
     49program controlled digital computer for only $16,250 in the minimum
     50configuration." This configuration consisted of the CPU and a Flexowriter only.
     51This machine was the successor of the LGP-30 (1st generation, 1956, also build
     52by Schoppe & Faeser in Germany as a licensed product). The LGP-21 is very rare
     53- only about 100 machines were built in Germany. Even rarer is the magnetic
     54tape unit of which only 5 known units were built. The machine in the museum has
     55serial number 4.</p>
    4456
    4557<div class="box left clear-after">
     
    4759                <p class="bildtext small">The external memory of the LGP-21 are perforated papertapes, which are scanned mechanically of the Tally-tape reader. The magnetic tape drive and other external drives were added in the late 60s.</p></div>
    4860               
    49 The (rotating) disc (with fixed heads) is used as storage and clock
    50 generator. Our installation, as shown above, features a lot of
    51 periphery: A magnetic tape station (1/4" tapes), paper tape
    52 reader/puncher, an additional hard disc and a flexowriter (printer and
    53 manual tape puncher for data/programs).<br>
    54 Once again, the reperation will be a challenge. More information will be
    55 disclosed later.</p>
     61<p>As external storage the LGP-21 employs a paper tape system using Tally
     62papertape readers. The magnetic tape unit and two external disks with a
     63capacity of about 8000 words each were added in the late 1960s.<br>
     64
     65A rotating disk serves as the machine's main memory and clock generator. It
     66rotates with 1475 RPM and holds 4096 words of 32 bits each which equals 12 kB,
     67a reasonable size back then. The disk contains 64 data tracks, four timing
     68tracks and tracks for three registers (accumulator, instruction register and
     69counter register). The mean write density is about 10 Bit/mm (about 1/200th of
     70today's disk drives).<br> Here you can see a picture of the
     71<a  class="popup" href="/shared/photos/rechnertechnik/lgp21-platte.jpg"><b>LGP-21 disk drive</b></a><br>
     72
     73The LGP-21 supports 23 different instructions - enough to program typical
     74scientific applications.<br>
     75
     76Repairing the machine turned out to be quite a challenge. Having two machines
     77of this type helps a lot.
     78
     79More information about this interesting and rare system will follow.</p>
     80
     81
     82               
     83</p>
    5684
    5785       
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