website/content/museum/didaktik-gama.md

---
title: Didaktik Gama
categories:
- Computers
types:
- Home Computer
origins:
- Slovakia
years:
- '1987'
cpus:
- Z80A
params:
  name: Gama
  company: /companies/didaktik
  company_name: Didaktik
  specs:
  - label: NAME
    value: Gama
  - label: MANUFACTURER
    value: Didaktik
  - label: TYPE
    value: Home Computer
  - label: ORIGIN
    value: Slovakia
  - label: YEAR
    value: '1987'
  - label: END OF PRODUCTION
    value: Unknown
  - label: BUILT IN LANGUAGE
    value: Spectrum BASIC interpreter
  - label: KEYBOARD
    value: Full-stroke keyboard, Sinclair style, 40 keys, reset button
  - label: CPU
    value: Z80A
  - label: SPEED
    value: Unknown
  - label: RAM
    value: 80 KB (16 KB + 2 x 32 KB)
  - label: ROM
    value: 16 KB
  - label: TEXT MODES
    value: 32 columns x 24 lines
  - label: GRAPHIC MODES
    value: 256 x 192 dots
  - label: COLORS
    value: '8'
  - label: SOUND
    value: Beeper (1 voice, 5 octaves)
  - label: SIZE / WEIGHT
    value: 27 (W) x 16.5 (D) x 3.6 (H) cm
  - label: I/O PORTS
    value: i8255 interface, expansion bus, TV and monitor output, tape-recorder sockets
  - label: BUILT IN MEDIA
    value: None
  - label: POWER SUPPLY
    value: External PSU
  - label: PRICE
    value: 6000,- Kcs (Kès) (1987, Czechoslovakia)
  tabs:
  - photos
  - hardware
  - links
  photos:
  - title: GREY VERSION
    subtitle: ''
    text: ''
    image: null
  - title: SIDE VIEW
    subtitle: ''
    text: ''
    image: null
  - title: GREY KEYBOARD
    subtitle: ''
    text: ''
    image: null
  - title: BLACK KEYBOARD
    subtitle: ''
    text: ''
    image: null
  - title: REAR CONNECTORS
    subtitle: ''
    text: |-
      From left to right:

      • Parallel I/O connector\
      • Spectrum compatible I/O Bus connector\
      • DIN plug used simultaneously for external power supply and tape recorder connexions\
      • Monochrome composite video output\
      • TV aerial output.
    image: null
  - title: INSIDE EXPLAINED
    subtitle: ''
    text: |-
      **(1)** TV aerial output connector\
      **(2)** Monochrome composite monitor output connector\
      **(3)** DIN plug used simultaneously for external power supply and tape recorder connexions! (see the P.S.U. picture)\
      **(4)** Ferranti ULA chipset (Same as Sinclair original version)\
      **(5)** Spectrum compatible I/0 connector\
      **(6)** Z80 microprocessor labelled ZILOG\
      **(7)** Sinclair Operating System and BASIC interpreter 16 KB ROM\
      **(8)** Parallel interface (unusual) connector\
      **(9)** 8255 Input/Output dedicated chip\
      **(10)** 64 KB japanese RAM chips bank\
      **(11)** 16 KB East-European RAM chips bank\
      **(12)** Power LED (green), Bank switching LED (red) and reset switch\
      **(13)** The keyboard cable is soldered on both sides. It is thus impossible to disconnect the keyboard from the motherboard\
      **(14)** TV RF modulator
    image: null
  - title: INSIDE GREY VERSION
    subtitle: ''
    text: The desing of the motherboard is slightly different from the black one.
    image: null
  - title: FERRANTI ULA CLOSEUP
    subtitle: ''
    text: Thanks to Martin Kriz for this picture
    image: null
  - title: INSIDE CLOSEUP
    subtitle: ''
    text: Thanks to Martin Kriz for this picture
    image: null
  - title: THE BOX
    subtitle: ''
    text: ''
    image: null
  - title: IN ITS BOX
    subtitle: ''
    text: Inside its cardoard box, the Gama was enclosed into a white plastic case.
    image: null
  - title: USER MANUALS
    subtitle: ''
    text: ''
    image: null
  hardware:
  - title: JOYSTICK 'MADE IN CZECKOSLOVAQUIA'
    subtitle: ''
    text: ''
    image: null
  links:
  - title: Clube do TK90X
    url: http://www.tk90x.com.br
    text: Brazilian site dedicated to the TK90 and other Microdigital systems
  - title: Here, you can buy several Didaktik models and peripherals.
    url: http://www.kompaktservis.cz
    text: Site in Czech language. Try e-mail
  - title: Home Computer Museum
    url: http://www.homecomputer.de/pages/f_sinclair.html
    text: Stephan has a lot of Spectrum clones with wonderful pictures
  - title: Sinclair Nostalgia Products
    url: http://www.algonet.se/~rsm/zx/zxclones.html
    text: Impressive list of ZX Spectrum clones with useful infos
  - title: ZX Spectrum in the 21st Century
    url: http://tarjan.uw.hu/zxclones_en.htm
    text: Nice review of modern Spectrum clones
  comments:
  - author: baze (Slovakia)
    date: Saturday 25th July 2020
    text: At one point there was an urban myth that Didaktik Gama had an alternative Cyrillic character set combined with Czech/Slovak diacritic marks. I guess the sentence "It has only latin character set" is meant to convey that this urban legend is not true. Didaktik Gama never had anything other than a regular Latin character set, although it used a bolder font.
  - author: Kubik
    date: Wednesday 29th June 2016
    text: |-
      The voltages are +5V and approx +20V - the second voltage isn''t stabilized in power supply and may vary. Didaktik Gama stabilizes it to +12V used for video signal circuitry.\
      The memory chips are of various origin. I have seen bulgarian CM8164P, russian KR565RU5G (transcribed from cyrilics), or Samsung KM4164B. I wouldn''t be surprised to see czech MHB4164 in some variants.\
      The 16Kb memory chips are different to the ones used in ZX Spectrum. The chips used in Didaktik Gama need just one voltage, 5V. I have seen Fujitsu MB8118, or Intel D2118.
  - author: Martin
    date: Friday 13rd December 2013
    text: Hello Damian, it is 5V and 12V, not 24V.
  - author: Damian
    date: Friday 22nd June 2012
    text: Didaktik gamm power supply is +5v and +24v
  - author: Petr (Czech Republic)
    date: Wednesday 5th November 2003
    text: Hello, I still have this cool machine and now I am working on a connection with a PC for sending a picture from Didaktik & showing it in a window on the PC. Nice time to U all!
  related:
  - /museum/didaktik-kompakt
  - /museum/didaktik-m
  - /museum/microdigital-tk-90x
  - /museum/microdigital-tk-95
  - /museum/robik
  - /museum/spica-ines
  oc_id: 463
  source:
    url: https://web.archive.org/web/20230528105857/http://www.old-computers.com/museum/computer.asp?c=463
    date: '2023-05-28'
---

This was a Slovak Spectrum clone made by [Didaktik Skalica Ltd](http://www.didaktik.sk/i.html). in communism times (1987). It offered 80 KB RAM.

As all Z80A based computers, it was not possible to address more than 64k. So the Gama computers used a bank switching technique, with two 32k additional RAMs. There was even a LED on the case, which indicated if the RAM have been switched or not!

The Gama computers had a built-in paralel i8255 interface. They used the original Ferranti ULA and had russian made memory chips.

The Gama computers were not fully compatible with the original [Sinclair Spectrum](/museum/sinclair-zx-spectrum/) due to some system variables differences.

In fact several models were made.

\- The first one was black and, as it was made in 1987, it is often called Gama'87. It had a bank switching bug : if you switched the banks and the RAMTOP variable was above 32768, then the computer simply crashed...

\- In 1988, the Gama'88 was launched (grey case). It's main difference is that the bank switching bug was repaired.

\- One year later, the Gama'89 (guess why) was released because the '88 model was still quite buggy. Some bugs in ROM were corrected and hardware was a little bit changed, so the compatibility was improved. It has only latin character set and a print routine was implemented in ROM. The Gama'99 was the last and the best model of the Gama serie, it was manufactured up to 1992.

---

**Branislav Bekes sent us info and specs for the Gama'89 :**\
CPU Z80A, ROM 16k, RAM 80k bankswitched, graphic mode 256x192 with 8 colors, text mode 32x24. Two bottom lines were reserved for interpreter. Sound 1bit beeper.\
I/O ports : TV OUT, VIDEO OUT, TAPE IN/OUT shared with POWER SUPPLY connector. Expansion slot and 8255 interface. Power supply is external and offers +5V and +12V.

**About the Ram switching, Abraham add:**\
The memory banks switching in GAMA was used for "tricks", like enabling on GAMA the AY sounds and music in games designed originally for ZX 128, taking game screenshots, enhancing the copy programs and many more things.