Building a 6502 Laptop: The LT6502 Project

The LT6502 project represents a fascinating intersection of retro computing nostalgia and modern maker ingenuity. TechPaula has embarked on an ambitious journey to create a fully functional laptop centered around the venerable 6502 microprocessor—the same chip that powered the Apple II, Commodore 64, and countless other iconic computers of the late 1970s and early 1980s.

The Vision Behind LT6502

The project began with a simple realization: working with the PC6502 project was enjoyable, but having a tower of PCBs on the sofa wasn't practical. This led to the natural evolution toward creating a self-contained laptop form factor. The design philosophy embraces simplicity while packing impressive capabilities into a compact package.

Technical Specifications

The LT6502 boasts an impressive array of features for a 6502-based system:

• 65C02 processor running at 8MHz
• 46K RAM for BASIC programs and data
• Built-in BASIC interpreter in ROM
• 65C22 VIA for timers and I/O operations
• 9" display with built-in font and simple graphics capabilities
• Compact Flash storage for program persistence
• 10,000mAh battery with USB-C charging
• Full keyboard integration with serial console support
• One internal expansion slot for future enhancements

Development Timeline and Progress

The project has seen rapid and impressive development since its initial commit in November 2025:

Early Phase (November-December 2025): The foundation was laid with complete PCB and schematic designs, followed by the arrival of manufactured PCBs. Initial power-up tests confirmed all voltage levels were correct, validating the electrical design.

Board Bring-up (January 2026): The core functionality was established sequentially—first verifying ROM and RAM operation, then adding console support. The VIA and ACIA chips were integrated, enabling communication with the keyboard. By January 5th, the keyboard was fully integrated into the firmware, eliminating the need for a separate console for input.

Feature Expansion (January 2026): Compact Flash support was added, along with a beeper for audio feedback. The system successfully ran from battery power, demonstrating the viability of the portable design. Display integration began with a 4.3" RA8875-based screen, though attempts to use a LT7683-based display were unsuccessful.

Case Development and Software Features (January-February 2026): Case-related work encountered some real-world challenges, leading to design refinements. The CPLD was tweaked to optimize FTDI read/write speeds. BIOS development progressed with the addition of a startup beep and file management functions. By February 8th, SAVE, LOAD, and DIR commands were implemented for Compact Flash operations, followed by additional graphics commands.

Final Assembly (February 2026): The case was successfully assembled, bringing the project closer to its final form.

Memory Architecture

The memory map demonstrates thoughtful organization for a system of this complexity:

• 0x0000-0xBEAF: 48,816 bytes of RAM, including zero-page and space for BASIC operations
• 0xBE00-0xBFFF: 512 bytes for peripheral mapping
• 0xC000-0xFFFF: 12,288 bytes of ROM containing EhBASIC, eWoz monitor, bootstrap code, and 6502 vectors

Enhanced BASIC Implementation

One of the most impressive aspects of the LT6502 is the extensive set of commands added to the EhBASIC interpreter. These enhancements transform the system from a simple BASIC environment into a capable graphics and I/O platform:

• BEEP P,L: Generates audio tones with configurable pitch and duration
• CIRCLE X,Y,R,C,F: Draws circles with color and fill options
• CLS: Clears both graphics and text modes
• COLOUR: Sets text color using 8-bit RGB values
• DIR: Lists files on the Compact Flash card
• ELIPSE X,Y,RX,RY,C,F: Draws ellipses with customizable dimensions
• LINE X,Y,EX,EY,C: Draws lines between coordinates
• LOAD/SAVE: Manages program storage on Compact Flash
• MODE: Switches between text and graphics modes
• OUTK: Outputs text to the keyboard's 8-character display
• PLOT X,Y,C: Plots individual pixels
• SQUARE X,Y,EX,EY,C,F: Draws squares with fill options
• WOZMON: Provides access to the enhanced monitor for low-level debugging

Hardware Integration Challenges

The project documentation reveals several interesting technical challenges that were overcome:

Display Selection: The initial attempt to use a LT7683-based display failed, leading to the successful integration of a RA8875-based 4.3" display. Future plans include attempting a larger 10.1" RA8889-based screen or falling back to a 9" RA8875 option.

Keyboard Integration: Getting the internal keyboard working required significant firmware development, but the result is a seamless user experience where typing on the physical keyboard directly inputs into BASIC programs.

CPLD Optimization: The CPLD was modified to slow down FTDI read/write operations, likely addressing timing issues that emerged during testing.

The Case Design

The 3D-printed case represents a significant achievement in itself. Multiple views show a well-thought-out enclosure that accommodates all components while maintaining portability. The design allows access to internal components for maintenance and expansion while providing a clean, professional appearance when closed.

Future Development

The project's to-do list indicates ongoing development, with the primary focus being the integration of a larger display. The expansion slot also suggests plans for additional hardware capabilities in the future.

Significance and Impact

The LT6502 project stands as a remarkable achievement in the maker community. It demonstrates that with modern manufacturing capabilities, open-source tools, and determination, it's possible to create sophisticated computing devices based on vintage architectures. The project serves multiple purposes:

• Educational Value: Provides hands-on experience with low-level computing concepts
• Preservation: Keeps the 6502 architecture alive and relevant
• Innovation: Shows how classic designs can be enhanced with modern features
• Inspiration: Encourages others to explore retro-computing projects

The project's open-source nature, with complete schematics, PCB designs, and firmware available on GitHub, ensures that others can learn from and build upon this work. The detailed status updates provide valuable insight into the iterative development process, including both successes and setbacks.

Conclusion

The LT6502 represents more than just a technical achievement—it's a testament to the enduring appeal of the 6502 architecture and the creativity of the maker community. By combining vintage computing principles with modern manufacturing and design techniques, TechPaula has created a unique device that bridges computing history with contemporary maker culture. As the project continues to evolve, it will undoubtedly inspire further innovation in the retro-computing space and serve as a valuable resource for anyone interested in understanding how computers work at their most fundamental level.

For those interested in following or contributing to the project, the complete source code, schematics, and documentation are available on GitHub. The project exemplifies the collaborative spirit of open-source hardware development and the ongoing fascination with the computers that helped launch the personal computing revolution.