Guide to the TD4 4-bit DIY CPU

The developer's experience with the TD4 4-bit CPU kit, sourced from Aliexpress, reveals the challenges of working with limited computing resources. The kit's 16 bytes of program ROM and 2 registers forced the developer to think creatively when writing simple programs. For instance, they had to manually assemble and update jump addresses to get a counting program to work. The TD4's instruction set, which includes commands like ADD, MOV, IN, OUT, JNC, and JMP, is implemented using a combination of combinatorial logic chips and discrete components.

The TD4 kit, designed by wuxx and documented on GitHub, demonstrates the educational value of DIY CPU projects. By building and programming the TD4, developers can gain hands-on experience with computer architecture and digital electronics. The project's use of surface-mount diodes, IC sockets, and a USB connector for power also highlights the importance of careful soldering and assembly.

The developer's experiments with the TD4, including simple programs like a blinking LED and a counting program, showcase the kit's capabilities despite its limitations. The TD4's 4-bit architecture and 16-byte program ROM impose significant constraints, but the developer's creative problem-solving and use of modular arithmetic demonstrate the potential for innovative solutions.