website/content/museum/didaktik-gama.md

title, categories, types, origins, years, cpus, params

title	categories	types	origins	years	cpus	params
Didaktik Gama	Computers	Home Computer	Slovakia	1987	Z80A	name image company company_name specs tabs forum_thread photos hardware links related oc_id source Gama /media/museum/photos/didaktik_gamma_system_1.jpg /companies/didaktik Didaktik label value NAME Gama label value MANUFACTURER Didaktik label value TYPE Home Computer label value ORIGIN Slovakia label value YEAR 1987 label value END OF PRODUCTION Unknown label value BUILT IN LANGUAGE Spectrum BASIC interpreter label value KEYBOARD Full-stroke keyboard, Sinclair style, 40 keys, reset button label value CPU Z80A label value SPEED Unknown label value RAM 80 KB (16 KB + 2 x 32 KB) label value ROM 16 KB label value TEXT MODES 32 columns x 24 lines label value GRAPHIC MODES 256 x 192 dots label value COLORS 8 label value SOUND Beeper (1 voice, 5 octaves) label value SIZE / WEIGHT 27 (W) x 16.5 (D) x 3.6 (H) cm label value I/O PORTS i8255 interface, expansion bus, TV and monitor output, tape-recorder sockets label value BUILT IN MEDIA None label value POWER SUPPLY External PSU label value PRICE 6000,- Kcs (Kès) (1987, Czechoslovakia) photos hardware links 458 title subtitle text image GREY VERSION /media/museum/photos/didaktik_gama_greysystem_s1.jpg title subtitle text image SIDE VIEW /media/museum/photos/didaktik_gama_greyside_s1.jpg title subtitle text image GREY KEYBOARD /media/museum/photos/didaktik_gama_greykeyboard_s1.jpg title subtitle text image BLACK KEYBOARD /media/museum/photos/didaktik_gamma_keyboard_1.jpg title subtitle text image REAR CONNECTORS 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. /media/museum/photos/didaktik_gama_greyrear_s1.jpg title subtitle text image INSIDE EXPLAINED **(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 /media/museum/photos/didaktik_gamma_inside_1.jpg title subtitle text image INSIDE GREY VERSION The desing of the motherboard is slightly different from the black one. /media/museum/photos/didaktik_gama_greyinside_s1.jpg title subtitle text image FERRANTI ULA CLOSEUP Thanks to Martin Kriz for this picture /media/museum/photos/didaktik80_inside.jpg title subtitle text image INSIDE CLOSEUP Thanks to Martin Kriz for this picture /media/museum/photos/didaktik80_inside_2.jpg title subtitle text image THE BOX /media/museum/photos/didaktik_gama_box_s1.jpg title subtitle text image IN ITS BOX Inside its cardoard box, the Gama was enclosed into a white plastic case. /media/museum/photos/didaktik_gama_greyplasticbox_s1.jpg title subtitle text image USER MANUALS /media/museum/photos/didaktik_gama_manuals_s1.jpg title subtitle text image JOYSTICK 'MADE IN CZECKOSLOVAQUIA' /media/museum/hardware/didaktik_joystick_1.jpg title url text Clube do TK90X http://www.tk90x.com.br Brazilian site dedicated to the TK90 and other Microdigital systems title url text Here, you can buy several Didaktik models and peripherals. http://www.kompaktservis.cz Site in Czech language. Try e-mail title url text Home Computer Museum http://www.homecomputer.de/pages/f_sinclair.html Stephan has a lot of Spectrum clones with wonderful pictures title url text Sinclair Nostalgia Products http://www.algonet.se/~rsm/zx/zxclones.html Impressive list of ZX Spectrum clones with useful infos title url text ZX Spectrum in the 21st Century http://tarjan.uw.hu/zxclones_en.htm Nice review of modern Spectrum clones /museum/didaktik-kompakt /museum/didaktik-m /museum/microdigital-tk-90x /museum/microdigital-tk-95 /museum/robik /museum/spica-ines 463 url date https://web.archive.org/web/20230528105857/http://www.old-computers.com/museum/computer.asp?c=463 2023-05-28

This was a Slovak Spectrum clone made by Didaktik Skalica Ltd. 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 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.

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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.