Readers entering their fourth decade on this planet might remember the name "3Dfx Voodoo", the graphics card responsible for kickstarting the 3D gaming revolution. Thirty years down the line, YouTuber PixelPipes revisits this revolutionary piece of hardware as a modded version loaded with 12 MB of VRAM (up from 4 MB) and an extra texture mapping unit — courtesy of Romanian hardware reverse-engineer "sdz" (SDZ).
PixelPipes' video goes into detail about how the installed mods massively improve the Voodoo card's performance, and it's worth a watch. The main takeaway is that, once accompanied by a fast enough CPU (for the time), apart from clock speed considerations, the performance profile of the modded card inches close to that of a 3Dfx Voodoo 2, the successor card that's arguably better known worldwide.
If that's surprising all by itself, the underlying reason is even more so: the Voodoo's initial design actually used a multi-point bus layout between some of its chips. Let's quickly dissect that. A standard Voodoo card had one Frame Buffer Interface (FBI) chip that processed polygons and built the final picture, alongside a Texture Mapping Unit (TMI) chip that handled textures, with bilinear filtering.
The bus between those chips was 2 x 16 bits — one line for reads and one for writes — but the write bus could access up to three TMUs, with the return path by way of a one-way serial connection between each TMU unit available, until all data was obtained through TMU 0. This is illustrated in the diagram below.
If you thought that layout was unexpectedly forward-thinking on the part of 3Dfx's engineers, the fact that the Voodoo supported SLI off the bat is even more so. Several companies produced their own souped-up versions with extra TMUs, extra RAM, expansion daughterboards, SLI (even in one card!), or all at once. Quantum3D was reportedly the leading maker of these configurations for professional markets and arcade machines.
While on the topic of memory, the FBI and TMU on a regular card each had 2 MB of dedicated VRAM, for a total of 4 MB. That explains the 640x480 resolution limitation, as that's how much you could reasonably fit within the 2 MB frame buffer, alongside work data. Wiring more RAM to each chip meant you could use the 800x600 resolution and have a roomier space for texture data.
The modded card designed by SDZ and available as an open-source project uses the FBI connected to two TMUs, with 4 MB of RAM for each chip, for a grand total of 12 MB. PixelPipes notes that this variant isn't directly supported by Quantum3D drivers, precluding games that relied on Direct3D from working altogether. The 3Dfx-specific Glide API remains functional, though, and after massaging some environment variables in autoexec.bat, he got the card running some games.
One of the PixelPipes' immediate conclusions was that the original Voodoo design was CPU-constrained in practice. Testing the modded card with a period-appropriate Pentium machine didn't yield a significant uplift versus an OG card, but once moved to a Pentium II box, the modified Voodoo came into its own, offering speed boosts of 40 to 60%. That's quite the feat by "just" adding another texture mapper and RAM. Incidentally, the Voodoo 2's base layout was quite similar, except that it ran at a higher clock speed, 90 MHz instead of 50 MHz.
If you thought the deep dive was interesting, do sit and watch the PixelPipes video in its entirety. For my part, I still remember in detail the day when I first laid my eyes on a Voodoo 2 running Quake and was utterly gobsmacked, witnessing buttery smooth graphics at a high resolution, with clean textures. That seemed unreal (pun unintended) at the time, especially having witnessed Nvidia's first card, NV1, at a trade show just a short while before and coming out relatively unimpressed.
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