Okay, back with good news, the card works nicely and games work as they did before the upgrade.
The card itself is a generic 8mb reference design, probably a Pine or something similar, I couldn't see any branding on it other than 3Dfx:
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I forgot to take any pictures of it before the upgrade because there are some good ones online already, but the front didn't change.
It now detects as a 12MB card in the driver's control panel:
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The chips used can be found on thebay by searching for the part code in RichB93's original post. I think they are pretty old stock and were just loose in an anti static bag so I Recommend cleaning them and making sure the legs are equal height before proceeding. By getting them at an even height, and cleaning the chips and board, using solder paste, I expect they should go on properly without much trouble. I made the mistake of hand soldering these using my TS100 iron and an angled tip. It worked but it took a while before I was confident were no gaps or bridged pins.
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See there's a gap at the top / front of the picture? While I was tinning and cleaning the pads, one of them fell off. Thankfully, this appears to be the only one that I could find that doesn't route anywhere.
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I did find a few spots where under a microscope / zoomed macro camera shot, it looked like there were gaps between the SOJ chips and the pads - maybe they're okay underneath but I didn't want to take chances, so I even broke out the leaded solder and went over them until there was a clear join between the board and the chip.
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So far, I've tested it with Unreal, Carmageddon 2 and glQuake, each of which works nicely - though I do get some HUD flickering in glQuake, I'm not sure what's causing that. I went from Voodoo 1 to TNT2 Ultra back in the day, I'm not as familiar with the Voodoo2