ATX-80: A ZX-80 Computer Clone Using an ATmega8 Processor
owl writes:
http://www.breatharian.eu/hw/atx80/index_en.html
The ATX-80 is a microcomputer derived from the ZX-80, with an ATmega8 processor. It does not emulate code, but replaces the original computer with custom code with similar functionality in AVR assembly. It allows output of the video to a VGA monitor or to a PAL/NTSC television. BASIC programs can be stored in internal EEPROM, internal Flash or external EEPROM memory (32 memory slots) and also transferred between PC and memory. The advantages are easy construction and small size. It can be used as a small inexpensive computer for teaching basic BASIC programming. Includes 32 sample programs.
[...] The original intent of the project was to create a computer with similar features and technical limitations as the original ZX-80. That is, a fully functional BASIC interpreter with only 1 KB of RAM and as close to 4 KB of ROM as possible. The project was also conceived as a study of the original ZX-80 BIOS ROM. It must be admitted that the original ZX-80 BIOS was an admirable creation. In addition to being very innovative, it was created with a high optimization of code size, and although this required a considerable amount of clarity in the flow of data between functions, the author maintained an overview of the code with minimal errors. I have tried to keep the functionality of the original code as accurate as possible and commented my code in detail, which can be a useful addition to explain the BIOS functionality. The ZX-80 BIOS is a very useful and informative study material and, despite its age, deserves more attention as an admirable work.
Read more of this story at SoylentNews.