Dubna 48K

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Dubna 48K

Type	Home computer
Released	1991
Discontinued
Processor	analogue of Zilog Z80 @ 1.875 MHz
Memory	48 kB
OS	Sinclair BASIC

2. Mainboard

3. CPU and ROM

4. RAM

Dubna 48K is a Soviet clone of ZX Spectrum home computer. It was based on an analogue of Zilog Z80 microprocessor. Its name comes from Dubna, a town near Moscow where it was produced, and "48K" stands for 48 kilobytes of RAM.

According to the manual, this computer was intended for:

Studying principles of work with PC
Different kinds of calculations
"Intellectual games"

By the time this computer was released (1991), there were already much more powerful x86 CPUs and commercially available advanced operating systems, such as Unix, DOS and Windows. Dubna 48K had only built-in BASIC interpreter, and loaded its programs from a cassette recorder, so evidently, it couldn't run any of modern operating systems, and as such, wasn't suitable for "studying principles of work with PC". However, Dubna 48K and many other Z80 clones, hopelessly outdated by that time, were largely introduced in high schools of Soviet Union. According to a contemporary who studied at a school in Chelyabinsk in the 1980s, they used wooden plates with keyboard drawn on them, as the schools lacked PCs greatly for the lessons of Computer Science. So even these outdated computers were considered as a great boon.

Moreover, most of the games for Z80 were already available for Nintendo's 8-bit game console, marketed in Russia under the brand "Dendy", and it was much cheaper, more reliable and easier way of playing games, so it became clear that Dubna 48K wasn't in much demand for home users.

1 Included items
2 Technical Details
3 Other facts
4 See also

[edit] Included items

Dubna 48K was shipped with the following units:

Main unit ("data processing unit", as stated on its back side), with mainboard and built-in keyboard
External power unit
Video adapter for connecting the computer to the TV set
BASIC programming manual
Reference book, including complete schematic circuit

Additionally, there were some optional items:

Joystick
32 cm (12") colour monitor

The computer could also connect to a ZX Microdrive, but such device was never included.

[edit] Technical Details

CPU: 1.875 MHz, 8-bit
RAM: 48 kB (in 16 KR565-series chips, see picture 4)
ROM: 16 kB (picture 3, two white chips in the middle)
Resolution: 256×192 pixels, or 24 rows of 32 characters each
Number of colours: 8 colours in either normal or bright mode, which gives 15 shades (black is the same in both modes)
RS-232 port
Power unit: 5V, 1.7 A
Dimensions of main unit: 52×320×255

[edit] Other facts

Dubna 48K has its case made of steel, while most other Spectrum clones had plastic cases.
There are people who buy used PCs like Dubna 48K. The reason for this is that these computers contain little amounts of gold and silver. For example, Dubna 48K contains (according to the manual) 1 g of gold, 3 g of silver and 0.1 g of platinum.
Due to lack of some chip, it could be replaced by several others. How to do this is described in the reference book shipped with the computer. For example, in the upper part of picture 4 you can see a small board with 3 chips installed in place of a single K555IR9.
Unlike Dubna 48K, most Z80 computers were assembled at home by amateurs, inspired by numerous articles in the Radio magazine. Programs for these computers, usually taking many pages (in binary codes) and BASIC programs were also printed in this magazine and had to be typed in manually.