If you are here maybe you know what is the Primo, but we will summarize here shortly. The PRIMO is a home computer which was developed in the 80's by a hungarian computer developer called SZTAKI. This is a 8 bit machine, with Z80 CPU. The hardware is realized modesty, but there are some interesting features in this machine. There are more than one product line. The series A has touch keyboard (works on capacitive way, this is the original Primo feeling). The series B has normal keyboard. There are tales about the series C and in this series was the ROM upgraded. We should take a mention about the Pro Primo, which has color screen. (There was a photo in a micro computer magazine near '86, and on this photo is a complete Pro Primo configuration, likely the one and only prototype.)

The different series was sold with different RAM configurations. The BASIC (and the operating system of-course) is in a 16K ROM, and only the size of the RAM was changed.


The Primo has only monochrome (black and white) screen with 256x192 resolution. (By the hardware manual the the Primo can works with the resolution 256x256, but this is only a hardware option, nobody used it.) The resolution 256x192 is the same resolution that the ZX Spectrum can do, but without colors. The pixel frequency is onther tan the Spectrum, It is not 7 MHz, but 7.5 MHz, so the CPU frequency is 3.75 MHz, but the displayed area horizontaly is little smaller. The screen memory is at the end of the RAM, and it uses only 6K. The hardware can do double buffering, the secondary screen memory is accesible under the first 8K. The series A has the following starting screen:


There is in the computer a speaker, which was called in the documentation "horn". This is a one bit sound generator like the PC Speaker in the PC-s. In that time, it was enough in a computer.


In the hardware manual there is a complete circuit diagram about the tape interface. In the first view, it seems overcomplicated, but later one can realize that it is very tricky. The interface is a creative and good solution, the loading is also safe when the records are noisy.


In the series A there is a "keyboard" which works by capacitive principles. This was realy only a board. It is from the electronical view a strike of genius, but it is mainly unusable. In the series B and C there are normal (usable) keyboards.


In the series A there is a lot of empty space on the motherboard. There was developed some I/O connection on the motherboard, but not imlemented in the A series. In all series are tape interface. In the B and C series are two additional connector implemented, they are:


Primo C was an experimental prototype, the precusor of the Pro/Primo.
Pro/Primo was prepared for the second School Computer Tender, with new desing (house, keyboard, and colors.


In the following we shortly describe the content of the Primo web site in the order of the buttons found in the left frame.

You can find here a lot of pictures about the Primo computers (A, B, and Pro Primo).

Its a story about the buy of a Primo computer, with a lot of brochures, the waranty card etc.

Some interviews, with some guys who were important in the Primo story.

There was a meeting with the developers of the Primo. Yo can find here some pcitures, and some text about it. Check the link at the bottom of this page!

DOS based Primo emulator. Some info about it on Előzmények, and download from Letöltés.

Windows based Primo emulator. Some info about it on Előzmények, and download from Letöltés

Some info about the usage of this emulator:

Ultimo.exe [/b] [/d] [/h] [/ma32|a48|a64|b32|b48|b64] [/t] [/w] [PTP file/PRI file]

/a : disable autostart if PRI file was loaded by the command line
/b : enable ROM/RAM banking (for example in case of Spectrum emulation)
/d : double size screen by default
/h : sound on at start
/i : RRGGBB - default text color
/m : Primo model (a32, a48, a64, b32, b48, b64, c64)
/p : RRGGBB - default backgorund color
/t : turbo switch on (3,75 Mhz)
/w : warp mode

You can only start PTP files from command line. You can start monitor with Esc key.

Open-sourced Primo emulator. You can download it from Letöltés.

Primo programs included into the bu22.com's Gamebase.

Primo A
Primo B
Primo C

Detailed info (ROM images, photos) about the A, B, and C types and the Pro/Primo.

Some info about the FDU-1109 which was an VC-1541 compatible floppy drive, with a built-in Z80 processor.

Info about the CDOS ("Commodore DOS") which was needed by the Primo if you used a VC-1541 compatible floppy drive with Primo.

Info and pictures about the joystick adapter. To use a Commodore/Atari joystick, you need to build this serial joystick adapter.

Info and pictures about the printer adapter.

Some interface cards for the Primo like a Testcard (GO-NOGO), a Network interface (LHIA-1) and a Serial interface (SHAA-1).

Another printer adapters with schematic.

Info and pictures about the Primo EPROM programmer, and Serial EPROM Storage. This second one was based on an interesting concept of serially reading EPROMs into the memory of the Primo. On the side of the Primo you need only a very short loader program, and you can use this accessory for multiple programs. So it's like a EPROM based tape, or like a FLASH based mp3 player? :)

Info about the implementation of memory banking. Needed for the Spectrum emulator and for the CP/M.

Info about the modification of the Turbo mode (2,5 MHz -> 3,75 MHz)

Description of the building of an external Hall-keyboard for the Primo.

Primo PIO
Description and pictures about the Primo Programmable I/O Interface.

On this page you can find a lot of info about the CP/M developed for the Primo. For example, how to build the hardware modifications, the EPROM images, and the original CP/M which was the basis of the Primo CP/M. At present we don't have the original CP/M for the Primo, maybe it's lost forever.

Syster and Varyter was the other product line which was developed by Cosy, the same company that developed Primo. The Primo could be connected to these machines to access their resources by an interface card.

Info about the file formats used by the Primo.

Tools to convert audio files to binaries and back.

wavview - show the WAV file on the screen
ptp2wav - converts PTP back to a WAV file.
wav2ptp - converts WAV file to PTP file.
pri2ptp - Conversion between the two formats PTP (primo tape program) and the PRI (simple Primo file from a CDOS floppy disk).
Another tool here is a CRC generating application used to compare whether you have the same program image in different disk and tape files. (Different PTP files may contain the same binary program, because the length of the data blocks varied by the copy programs.)

Some useful tools, for example, Win 98 DOS boot menu for the DOS emulator and the Star Commander to transfer disk images.

Pictures and downloadable programs from the original demo tape distributed with the Primo.

Primo games

Monitor, assembler and other development and productivity tools for the Primo.

Other software, which are not found in the previous two categories.

Evolution of games. How they came from ZX Spectrum, and go forward to the Videoton TVC (other Hungarian home computer).

Casette covers

Scanned books (a lot) in PDF format.

Magazine articles about the Primo.

Descriptions, advertising materials about the Primo.

Listák, tippek
Some type-ins, and tips from various magazines.

Graphical layout to print to foil, and cover the original keyboard on your computer. If you can print to foil in letter size then it will fit the keyboard of your Primo.

Building a Primo. Some PCBs were re-manufactured (motherboard and keyboard PCBs, too) and one of our members presented his experience about the development.

C típus
The Primo C type was only an experimental prototype. Its video adapter card was re-manufactured (a few cards only). A lot of info can be found here about this adapter card. Note that there was a lot of differences between Pro/Primo and Primo C. The Pro/Primo had the same video adapter card, but there was a specific connector for it on the CPU board. Pro/Primo had a different housing, keyboard, and EPROMs too, because it had a new BASIC with commands supporting graphics.

Színes Primo
A simple solution to have colors on the TV with a normal black-and-white Primo.

PS/2 keyboard
How to connect a PC PS/2 keyboard to the Primo.

The Primo guestbook.

You can write into the Primo guestbook here.

For more info, you can contact by e-mail: viktor.varga@gmail.com

(Viktor Varga)