A hardware enthusiast recently documented their attempt to build the “second world’s worst video card” using only TTL gates. This project aimed to create an even less practical graphics card than existing minimalist designs, highlighting the challenges of basic hardware construction.
Minimal VGA Output with Maximum Hassle
Despite intentionally using basic components, the project surprisingly achieved a functional, albeit flawed, VGA output. The core goal was to push the limits of simplicity in video card design.
Project Specifications
- Resolution: 800 x 600 (SVGA) @ 60Hz, accessible resolution of 400 x 300 in monochrome.
- Components: 21 integrated circuits, including counters, NAND gates, EPROM, and SRAM.
- Character Sets: Up to four sets of 255 characters, utilizing a 1-Mbit EPROM.
Challenges and Limitations
The build process, relying on thin wire on a protoboard, proved to be difficult. The final product suffered from various issues:
- Visual Artifacts: Tri-state buffers and a basic counter setup led to glitches and instability.
- Memory Conflicts: Image distortions occurred during memory writes because simultaneous read/write operations were impossible.
- Environmental Sensitivity: Even USB cable noise significantly impacted the display.
- Character Issues: Limited ROM power and read times resulted in unclear characters.
- Unexplained Lines: Background lines appeared with no identifiable cause.
Overclocking and Unstable Performance
The HSYNC timer, a 12-bit counter rated for 12MHz, was pushed to 20MHz to increase the pixel clock. This overclocking introduced further timing errors and an unstable output. The card’s design involved comparing only the “ones” of counter outputs, which, while functional, introduced repeated signals.
Lessons Learned
This experiment demonstrates the difficulty of creating a stable VGA signal from basic TTL gates. The creator openly admitted the project was a “huge waste of time” and recommends using FPGAs instead. The project repository on GitHub offers conversion tools and test code for Arduino Mega, but it serves primarily as a cautionary tale.