https://olimex.wordpress.com/2015/01/12/retro-computer-puldin-the-only-bulgarian-8-bit-computer-developed-from-scratch/
http://atodorov.org/blog/2016/07/12/testing-the-8-bit-computer-puldin/
One of the main objectives of Puldin was full compatibility with IBM-PC. At the time IBM had been releasing extensive documentation about how their software and hardware works which has been used by Puldin's creators as their software specs. Despite IBM-PC using faster CPU the Puldin 601 had a comparable performance due to aggressive software and compiler optimizations.
The guy who wrote the Assembler BIOS and Basic ROM for Puldin – Todor Todorov became more famous with his virus works instead of what he did for Puldin
[...] in 1991, an international epidemic was diagnosed. One-hundred sixty documented Bulgarian viruses existed in the wild, and an estimated 10 percent of all infections in the United States came from Bulgaria, most commonly from the Dark Avenger.
Interesting.