website/content/museum/pravetz-8d.md

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

title	categories	types	origins	years	cpus	params
Pravetz 8D	Computers	Home Computer	Bulgaria	1985	CM630 - Bulgarian copy of the 6502	name image company company_name specs tabs forum_thread photos links oc_id source 8D /media/museum/photos/pravetz_8d_system_1.jpg /companies/pravetz Pravetz label value NAME 8D label value MANUFACTURER Pravetz label value TYPE Home Computer label value ORIGIN Bulgaria label value YEAR 1985 label value END OF PRODUCTION 1989 label value BUILT IN LANGUAGE Basic label value KEYBOARD Full stroke 57 keys Qwerty + cyrillic label value CPU CM630 - Bulgarian copy of the 6502 label value SPEED 1 mHz label value RAM 48 KB label value ROM 16 KB label value TEXT MODES 40 columns x 28 lines label value GRAPHIC MODES 240 x 200 (+ 3 text lines) label value COLORS 8 label value SOUND Programmable Sound Generator AY-3-8912 (from General Instruments)\ 3 voices, 8 octaves + white noise label value SIZE / WEIGHT 35 (W) x 25 (D) cm label value I/O PORTS Power supply, Expansion port, Printer/Centronics port, Tape-recorder DIN plug, RGB video out, RF TV out label value POWER SUPPLY Built-in power supply unit label value PERIPHERALS floppy disk unit, modem, dot matrix printer label value PRICE 420 levs (Bulgaria, 1985) photos links 962 title subtitle text image PRAVETZ 8D Thanks to joro_dramchev ( Ebay seller) for this picture. /media/museum/photos/pravetz_8d_system_3.jpg title subtitle text image CLOSE-UP Notice that the keyboard allows to use Latin or Cyrillic alphabet Courtesy **http://bulgariancomputers.freeservers.com/mycomputers/** /media/museum/photos/pravetz_8d_system_2.jpg title subtitle text image REAR CONNECTORS Thanks to joro_dramchev ( Ebay seller) for this picture. /media/museum/photos/pravetz_8d_system_rear.jpg title subtitle text image BOOT SCREEN Thanks to joro_dramchev ( Ebay seller) for this picture. /media/museum/photos/pravetz_8d_system_boot.jpg title subtitle text image INSIDE The hardware design was really close to the Atmos one. The same ULA chip (copy?) was used. Contrary to the Atmos, the PSU was located inside the case. Courtesy **http://bulgariancomputers.freeservers.com/mycomputers/** /media/museum/photos/pravetz_8d_inside_1.jpg title subtitle text image ARMENIAN SUPPORT LANGUAGE A tape program allows the use of specific Armenian characters. /media/museum/photos/pravetz_8d_armenian_1.jpg title subtitle text image ARMENIAN TRANSLATION Only for Armenian language specialists...... Thanks to **Mattias Persson** /media/museum/photos/pravetz_8d_armenian_2.jpg title url text Pravetz 8D page http://www.sofiaprint.com/pravetz8d_bul/Pravetz%208D_bul.html Interesting but in bulgarian... 988 url date https://web.archive.org/web/20230606134933/http://www.old-computers.com/museum/computer.asp?c=988 2023-06-06

The Pravetz 8D was a Bulgarian clone of the Oric Atmos featuring a Bulgarian version of the 6502 processor called CM630, 16 KB of ROM and 48 KB of RAM

The keyboard was almost the same as the original Atmos version, including a MK key, similar to the CTRL key, a C/L key allowing to display Cyrillic or Latin alphabets, and cursor keys. As in Pravets 82 (etc), the original lowercase characters were replaced by cyrillic characters and the C/L lock key, was the CAPS LOCK key of the Oric Atmos.

Like the original Atmos, The 8D had two modes of recording : Fast mode at 2400 bits/sec. and slow mode at 300 bits/sec.

The computer also featured a parallel Centronics interface and a user port. Pravetz provided a local dot matrix printer called "Petritch" but the popular Epson printers could be also connected to the 8D.

The "D" after Pravets 8 stays for "Äîìàøåí" (Domashen = For home use), and the idea was, that it should be used without having to buy any peripherals - monitor (which couldn't be connected through composite video to a Pravets 8D without modification) and FDD (cassete recorder used instead).

Floppy drives, modem and joysticks were also available. Floppy disk drives were very hard to find (in fact they appeared only in the early nineteens). They were a modification of the Pravetz 82 FDDs but with a built-in controller, making them two times bigger. Probably that was one of the reasons why Pravetz 8D never achieved the popularity ot Pravetz 8 (despite of the 3 times lower price).

There were in fact two ways to have floppy disk drives for the Pravetz 8D. One was indeed to use Pravetz 82 FDD and to develop an additional controller + power supply (the schematic and firmware were published in "Computer for you" magazine). There was an operating system called DOS 8D, developed in Bulgaria by Borislav Zahariev.

Later, Pravetz factory decided to develop special FDD for the 8D, which was bundled with the controller and the power supply in a box twice bigger than the normal Apple ][ floppy. It came out on market when the production of the computer itself was finished! It used also modified version of DOS 8D for DIY floppy.

The computer was very well crafted and the survived systems often look as new.

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Contributed to this page : Bozhidar Stefanov, Jordan, anonymous visitor

Peter Petrov reports:

ROM
There are several rom images of the basic in Pravetz. If you wand disk emulation you need 8DControllerROM and use CALL#320 command.

RAM
With Basic you have 48 K RAM to work, but with this little schematics you can use additional 16K. The signals that you need for proper work are these. One trigger is used to form MAP signal, but second is free to use additional thing. If you realise schematis of disk controller below you can use these schematics together to load 8DDOS v2.10 in additional RAM. You must use write operation in these adresses to use the controller:

#380 - writing in additional RAM - additional thing is off
#381 - writing and reading in additional RAM - additional thing is off
#382 - writing in additional RAM - additional thing is on
#383 - writing and reading in additional RAM - additional thing is on
for "additional thing" see Disk controller section

So, if you realise this little controller you can use:
FOR I = #C000 TO #CFFF : POKE I,0 : NEXT - clearing first 4K of additional RAM or you can move the basic interpreter in additional memory and use:
POKE #381,0
to go in RAM interpreter and make changes in it.

DISK CONTROLLER

If you have Apple ][ floppy drive and disk controller you can use this schematics to connect them to your Pravetz (Oric). The schematics is from two parts:
buffers
controller
The signals for proper work of the controller are here:
You can change the signal Q with changing the resistors of monovibrator 74LS123. The record of EPROM is here:
You must write it from addres #20 of the EPROM.

Connecting RAM controller and disk controller:
you can connect these controllers by this way:
pin 9 of 74LS74 is connecting to A8 addres bar of 2716 EPROM, so the "additional thing" is second page of the EPROM, where is the program of loading DOS 8D v.2.1 into additional RAM. (The record of the EPROM above is exatly for first and second page).

SOFTWARE

The versions of the DOS I have are:
Dos 8D v1.0 - you can use it if you realise only the schematics of the disk controller, but this versions loads in normal RAM, so it is unusable with long games.
Dos 8D v.2.1 - you can use it if you realise the two schematics and connect them. So - dos loads in additional RAM and you can use all the programs you have.
You can use regular Oric software in Pravetz 8D, but you have not regular letters. You have cyrillic letters instead. Changing of the keyboard maps is with Ctrl-T.
There are some games for Pravetz like SnakeByte, Tetris (exellent clone) and other. Most of them are from Bulgarian computer magazine "Computer for you". There is 80 column text editor, Disk copier program and the most beautiful - Borislav Zahariev ported BigMac Assembler from Apple ][ to Pravetz, so you can use if you realise schematics above. Soon I hope you will see this software here.

We need more info about this computer ! If you designed, used, or have more info about this system, please send us pictures or anything you might find useful.