A 7100

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robotron A 7100 (above) and robotron EC 1834 (below) on screen robotron K 7229.21
A 7100 computer during the final inspection at VEB Robotron Elektronik Dresden

The A 7100 was the first mass-produced 16-bit - personal computer of the GDR . It was introduced in 1985 and used a main processor of the type K1810WM86 . This was an exact replica of the Intel 8086 . Even so, the A 7100 was only limited in terms of PC compatibility . The device was manufactured by VEB Robotron from 1986 . The A 7150 was presented as the successor model in 1988 .

There was a graphics option for this computer, but it worked with a slow U-880 graphics processor and implemented GKS (see PHIGS ).

construction

The basic computer unit is 174 mm high, 486 mm wide and 451 mm deep. It weighs around 22 kg and has a RESET button and visual indicators for the status of the power supply and the fan. It can generate acoustic signals. A maximum of two 5¼ ″ floppy disk drives of the types K5600.20 ( one-sided , 80 tracks one-sided) or K5601 ( double-sided , 80 tracks two-sided) can be installed as mass storage devices in the desktop housing . Both drive models use the Modified Frequency Modulation recording method and a track density of 96 tracks per inch. You achieve an unformatted storage capacity of 0.5 Mbyte or 1 Mbyte per diskette . The manufacturer provided the K7672.01 and K7672.03 models with 104 keys each and the K7637.91 model with 106 keys as the external keyboard.

PC compatibility

In contrast to the IBM PC, in which the characters in the image repetition memory were only saved as ASCII and color codes, the A7100 saved the bit pattern of every character generated. That slowed down the simple text output visibly.

But that also had its advantages. There was a soft mode for scrolling, in which the user did not scroll line by line but by pixel. This made texts easy to read even while scrolling. By reprogramming the character generator, graphics could be generated in text mode.

In addition to the pixel-oriented text memory, there was also the graphic image repetition memory. It was possible to toggle between the two from the top line by line so that a combined display of graphics and text was possible.

The display was the responsibility of the controller for the graphic subsystem, which was controlled by a U880 . This was programmed with a specially loaded firmware.

The graphics memory was not accessible via the system bus. All graphic inputs and outputs were made via two port addresses, one of which received the data and the other contained the status. Special graphic commands could be transmitted and executed via the port combination. Their scope ranged from drawing points and lines with different line types to drawing complex bit patterns, lines, circles, polygons and filling them with predefined or definable patterns.

A wood processing company from the Karl-Marx-Stadt district developed an emulator for the A7100 that reprogrammed the KGS (graphic controller) and provided it with character and color code-oriented interrupt routines. With this emulator the A7100 was able to start MS-DOS . Under MS-DOS, however, the text memory was then at address 0x7800 instead of 0xB800, which is why programs that accessed the text memory hard instead of using interrupts could only run in specially patched versions. (e.g. Norton Commander , Borland Turbo Pascal 4.0)

When the emulator was running, the A7100 was no longer able to output graphics in conventional programs. This could be circumvented by a program triggering the KGS reset during processing, programming the graphics firmware, displaying the graphics and then saving the text firmware back again.

Technical specifications

  • Operating systems:
  • Processor: K1810WM86 (Soviet 8086 replica)
  • Clock frequency: 4.915 MHz
  • Main memory: 256 Kbytes, depending on the configuration up to 768 Kbytes
  • Drives: Two 5¼ " floppy disk drives (up to 720 kByte capacity)
  • Graphic:
    • 80 × 25 characters in text mode, monochrome
    • 640 × 400 pixels in graphics mode for the graphics variant

literature

  • Eckehart Stamer, Gerhart Ziese: The workstation computers A 7100 and A 7150 . 1st edition. Verlag Die Wirtschaft Berlin, 1988, ISBN 3-349-00306-0 .

Web links

Commons : Robotron A 7100  - Collection of pictures, videos and audio files