Didaktik Alfa
I received an eMail from Martin Petovsky the industrial designer of the Didaktik Alfa. Today he lives in Germany an added a lot of valuable first-hand information about the Didaktik Alfa:

• Production date: 1987
• Hardware-Design is based on the Hewlett-Packard 85
• People: Ing. Viktor Klemon (Project Manager), Ing. Roman Kiss (Hardware-Concept), Ing. Ludovit Bar�t (Construction), Mgr. Martin Petovsky (Design)

Martin Schotek found some infos about this computer and put them on his web-page [here].

According to Ousmane Keita the Didaktik Alfa was compatible with the Tesla PMD 85 (it was the same computer but in a different case) - this is confirmed by Martin Schotek. According to [MS] the "Alfa" is a clone of the Tesla PMD 85.1 with a simplified circuit diagram (no changeable ROM module with Basic, Basic was integrated in unused part of memory, simplified address decoder for I/O, changed address of tape interface). The Alfa-2 is a clone of the Tesla PMD 85.2 again with a changed circuit diagram. The Alfa-2 has a newer system software and basic. Also new: power on selftest, font support for all czech and slovak characters.

Some more news from Jan Ciger about the Alfa:
Didaktik Alfa - there are three versions of this machine. Blue case was usualy Didaktik Alfa 1 (the original model). Red case used by Alfa 2 and some refurbished pieces of the Alfa 1 - the machine was quite unreliable.

The third version was called Didaktik Beta and was actually improved version of Didaktik Alfa 2 in a brown (or dark green, not sure anymore - - it is more than 10 years I used one last time) case with a network support.

The HCM would certainly like any blue or brown Didaktik Alfa!!!

The Didaktik Beta network was a proprietary daisy-chain like design, used with another machine - PP 06 (basicaly an IBM PC clone, with 4MHz 8086 CPU). The PC machine was used to upload software to the Betas or to assist pupils with problems. Actually the whole thing was deployed most often as a computer lab for schools. The Alfa,Beta and PMD-85 machines were never home products, they were deployed only to schools and such.

There was one more Didaktik produkt - Didaktik Z (Zeta), but that wasn't a computer, it was an A4 plotter in a case similar to Didaktik Alfa (actually the computer case with the keyboard replaced by paper tray).

If anyone knows more details please let me know ...

Technical Overview:
Year: 1986 [confirmed]	CPU: Intel 8080A (2MHz)
RAM/ROM: 48kB / 8kB	Clone: Tesla PMD 85 / PMB-85.2
Colors: 4	Resolution: 288 x 256

The Didaktik Gama is the first machine of a whole series of sinclair clones made by the slovak company "Didaktik S". Unlike many of the other Sinclair spectrum clones from East Europe the Didaktik series uses the original Ferranti ULA. I am not sure if this means that the Didaktik series is a licenced Sinclair Clone. (Can anyone comment on that? According to Hynek Med this is unlikly.) At least the compatiblilty of the Didaktik should have been quite good.

The Didaktik Gama comes with a built in parallel interface and with 80kB RAM organized as 1x16kB + 2x 32kB.

One strange thing about the Didaktik Gama is that is only has ONE connector for power AND tape drive. So the power-supply has TWO plugs.

There are three versions of the Didaktik Gama named by their respectiv release years: '87 / '88 / '89. According to [SNP] the Gama '87 came in a black case and has some bank switching problemes that were corrected in with the Gama '88 (white case). The Gama '89 added cyrilic characters support. (can anyone confirm that?)

Technical Overview:
Year: 1987 [confirmed]	CPU: Zilog Z80/3.5MHz
RAM/ROM: 80kB / 16kB	Clone: ZX-Spectrum
Colors: 8	Resolution: 256x192

Surprisingly the Didaktik M has less RAM than the Gama - 64kB (?)and it can use only 48kB of it - but its compatibility is said to be enhanced.

Jan Ciger added this info:
The Didaktik M has only 48kB of RAM + 16kB of ROM, not 80 nor 64 (it is the same as Kompakt. Kompakt has only floppy added + different ROM). I still have my M in a working order. The RAM was reduced from the Gama series, because the bank switching circuitry was introducing incompatibilities with the original Spectrum and people complained about that. There was also very little software which was able to use the extended memory (I remember just some copying tools and assembler) There is also a 5 1/4 external floppy drive for M (works with Kompakt too, AFAIK)

Technical Overview:
Year: 1990 [confirmed]	CPU: Zilog Z80
RAM/ROM: 48kB / 16kB	Clone: ZX-Spectrum
Colors: 8	Resolution: 256x192

Another interesting feature is the EuroAV-Connector (SCART). This connector allows the Kompakt to be connected to a color monitor or color TV. In both cases the videosignal is R-G-B level and so the picture quality is much better than with composite video.

The Didaktik Kompakt has built in parallel port and two joystick connectors with regular plugs.

According to Jan Ciger there were two versions of the Didaktik Kompakt:

• Didaktik Kompakt (basic model) - 48kB of RAM, 3 1/2" floppy
• Didaktik Kompakt (improved model) - 128kB of RAM, 3 1/2" floppy, the AY sound module, SCART video output (similar to Spectrum 128, but I am not sure whether it is compatible, probably not).

According to [OCE] there are several different version of the PMD-85:

• PMD 85 (original version),
• PMD 85-1 (quite rare now because of the bad keyboard, first serial production, bad tape loading)
• PMD 85-2 (better keyboard and completly new software, new G-Basic 2.0, better tape loading, new schematic circuit, 5 COLORS)
• PMD 85-2A (new motherboard, new memory schematic circuit with free more 8kB for small routines),
• PMD 85-2B (Memory expanded from 16kB to 64kB),
• PMD 85-3 (new motherboard again, new TV PAL modulator, Czech and Slovak characters and russian azbuk version. If monitor 85-2 selected, fully compatible with PMDs 85-2x),
• Mato (simplified version in a smaller case).

As the HCM was able to aquire quite a few Tesla PMDs there is a lot more to tell:

Looking at the PMDs only the original PMD85 and the Mato seem to different - WRONG! I now own about 6 PMDs and only 2 are excatly the same. They rest differs with regard to the power-supply and TV connector even if the model number is exactly the same.

• jack of a PMD85-2A TV cable: You won't be able to find such a jack - Thanks again Mari�n for the cables!
• powersupply cable of a PMD85-2A:
• outlet jack of the powersupply:
• detail view power and tv PMD 85-2:
• detail view power and tv PMD 85-2A:

Rudolf Adamkovic wrote that "Tesla Mato it is not PMD85-2 in a smaller case but he is very simplified version, not compatible with PMD85-2. Software is not 100% compatibile with original PMD 85 and tape data format is too incompatible."

Technical Overview:
Year: 1985 [confirmed]	CPU: MHB 8080A (2MHz)
RAM/ROM: 48kB / 4kB	Clone: none
Colors: 4	Resolution: 288 x 256

Technical Overview:
Year: 198?	CPU: U880
RAM/ROM: 64kB / 4kB	Clone: none
Colors: b/w	Resolution: 320 x 255

• Computer was built-in into monitor (like Macintosh) with professional keyboard.
• Network available ("differential" - I think it means serial communication on TTL voltage).
• New extra graphic mode - higher horizontal resolution, all 8 bits in byte are used as a bitmap (usually only 6 bits were used as bitmap, two bits were attributes /flash and bright, or colors on later PMD versions/).
• No parallel interface built in, had connectors on processor-bus instead of it; parallel interface was part of "intelligent printer cable".

• possibility to boot from external ROM chip (used mainly to load printer drivers)
• possibility to boot from floppy (CP/M)
• login to network and boot from network (used to load Basic with network operations, redirected by the server to central discstation or printer queue; Basic-G in ROM had only tape operations).
• With no external ROM, no discdrive and no network, computer boots to Basic-G as default, not into Monitor as PMD did (can be changed by keypress).

Technical Overview:
Year: 1989	CPU: MHB 8080A (2MHz)
RAM/ROM: 32kB / 4kB	Clone: Tesla PMD 85.2
Colors: 4	Resolution: 288 x 256

• VIDEO [display],
• BASIC [interpreter],
• BASIC G [graphic Basic interpreter],
• GRAFIK [256 x 512 graphics],
• STAPER [printer],
• MINIGRAF [plotter]

• AMOS: "Autonomous Microcomputer Operating System"
• MIKROS: CPM clone OS for the IQ
• Pascal

It was used in almost all 8080 and Z80 based machines from Eastern Germany, in IQ151 and in many TNS machines from Slusovice. Here are som interstesing remarks from Dave about the IQ 151:

• Sure they [the IQ151] were able to warm a cup of tee
• Next thing what you could found was a 'custom-network'. Usually (as I remember our school class with IQ151s, but other schools were made pretty the same), every computer had it's own cassette player attached to it (slightly modified TESLA tape-deck - even after years these tape-decks are valuable for Hi-Fi people, because their quality was quite high). What I remember is that a teacher was able to load programs from his player to ALL IQ151 in the class and he was able to do this remotely from any IQ151 in class too. So he was able to explain something to student on student's comp and controll his own (teacher's) computer and it's tape-deck from student's place. I was really amazed by this.
• Some output devices more: CONSUL 2112 or 2113 (typewriters, probably), and SESTYK (telex machine)
• MINIGRAF was type of 0507, manufactured by ??? (Aritma, problably)
• The tape-deck mostly used was probably TESLA M710A
• The main suplier of programs for IQ-151 was Komenium.

Technical Overview:
Year: 1983/84	CPU: MHB 8080A (2MHz)
RAM/ROM: 32kB / 4kB	Clone: -
Colors: b/w	Resolution: 32-64 x 32-64 (text)

According to Jan Ciger there was also PP-03 (same as PP-01, but with color support) and PP-06 (basicaly an IBM PC clone, with 4MHz 8086 CPU)

Hynek Med added that "the PP-06 was a PC-XT clone with two 360k floppies (sometimes 20 MB MFM disk). I uses VUVT-DOS (a translation of MS-DOS), and an expantions bus which wasn't compatible with ISA."

Technical Overview:
Year: 198?	CPU: MHB 8080 (2MHz)
RAM/ROM: 64kB / 16kB	Clone: -
Colors: 8	Resolution: 256 x 256

Jiri Tomas Dolezal send me a nice mail with a picture:
"The SAPI was a BIG steel rack for "eurocards" (simillar as for IQ-151, but bigger and without the plastic case). One of them holds a power-supply, one is for communication with tape unit, one holds RAM, one holds processor, one holds ROM or BIOS, one holds connection for 8" floppy, another for paper-tape reader, another as TV output...
Processors used were 8080 and (later, for use with CP/M) Z-80. ROMs - usually was used only BIOS (I remember only that command for tape loading was K_L), or it was replaced by ROM with Micro-Basic, Forth, or CP/M, so they were accessed directly and not via tape or floppy.

The most common keyboard was this membrane one (you have it allready), later I saw various keyboards made by Consul (more professional and with more keys than the membrane ANK-1) and an old terminal without inner electronics, connected using cca 40 wires to SAPI as a keyboard and television output. Output was in text mode with various attributes (flashing, underline, bright), but I heard about fine graphic card (but never seen it).

I've found in our family album a photo of SAPI-1 machines (Tesla, former Czechoslovakia).
Notice the two different keyboards - the small membrane board ANK-1 (you have it on your www pages) and bigger Consul 259.11 (needs different keyboard driver in ROM) with microswitches on the right side.
As monitor, black and white TV (with Video-IN added) was used (I cannot recognise, if it is Pluto or Merkur, but more probably it is Merkur). Notice the size of "microcomputer". The TV is placed just on the computer case."

Technical Overview:
Year: 198?	CPU: Intel 8080A (2MHz)
RAM/ROM: 48kB / 16kB	Clone: -
Colors: b/w	Resolution: 40x20

• TNS-HC (=Home Computer)
• TNS-AT (PC AT Clone)

In Yugoslavia, Sinclair ZX Spectrum+ with DELTA label over the ZX Spectrum+ was sold, and was fairly common in Czechoslovakia. It was rumored that a lot of Spectrum+ was bought by a Sinclair employee, when Sinclair went down.