- Crude GPU design confirmed random glitches at any time when the system tried reminiscence writes
- iNapGPU struggled with environmental noise from easy USB cables
- A 12MHz counter overclocked to 20MHz induced fixed instability
An obscure challenge on GitHub reveals how a {hardware} hobbyist tried to assemble what he referred to as the “second world’s worst video card,” a text-mode graphics card utilizing solely TTL gates.
Working underneath the deal with Leoneq, he launched the “iNapGPU” repository to doc his experiment.
His aim was to outdo Ben Eater’s “world’s worst video card” by making one thing even much less sensible.
A minimal design that also exceeded true VGA limits
Regardless of intentionally utilizing crude strategies, he couldn’t cut back the output under a fundamental VGA decision.
The challenge specs checklist VGA output at 800 x 600 (really SVGA) @60Hz, with an accessible decision of 400 x 300 in monochrome.
The {hardware} was constructed from 21 built-in circuits, together with counters, NAND gates, and an EPROM working with a small SRAM.
By treating a 1-Mbit EPROM as a 1-bit reminiscence, Leoneq may load as much as 4 character units of 255 characters every.
Nonetheless, utilizing tri-state buffers and a fundamental counter association led to visible artifacts and poor stability.
Even when utilizing a low-capacity reminiscence and avoiding a microcontroller, the design nonetheless couldn’t degrade to one thing under VGA.
Leoneq admitted that the meeting course of was awkward, counting on 0.12mm wire on a protoboard quite than a printed circuit board.
He described the consequence as horrible and warned others to “use fpga as a substitute” to keep away from related frustrations.
The HSYNC timer was pushed by a 12-bit counter rated for less than 12MHz at 15V, but he pushed it to 20MHz to double Ben Eater’s pixel clock.
He in contrast solely the “ones” of counter outputs as a substitute of full numbers, a shortcut that launched repeated indicators with out breaking the show.
The unconventional method stored the cardboard practical, nevertheless it additionally revealed timing errors and unstable output.
This was by no means a viable graphics card as a result of picture glitches occurred at any time when it wrote to reminiscence, because it couldn’t write and browse concurrently.
Additionally, environmental noise, even from a close-by USB cable, distorted the show.
As well as, the characters lacked readability as a result of ROM energy and read-time limitations, whereas unexplained traces appeared within the background.
Leoneq brazenly labeled the picture as ugly and described the complete effort as a “large waste of time.”
Though the challenge demonstrated {that a} crude assortment of TTL gates may generate a usable VGA sign, it additionally reveals why fashionable designers favor programmable logic like FPGAs.
Leoneq’s repository supplies conversion instruments and take a look at code for Arduino Mega, however the effort appears extra like a technical joke than a sensible product.
