4MB VLB cards were always pretty rare, because they mostly came out at around the time people were buying PCI Pentiums, and they were crazy expensive. At one point the Diamond Stealth64 Video VRAM 4MB was the easiest one to get, but the memory upgrade modules usually had to be scavenged off the PCI version. The ATi Graphics Pro Turbo used to be slightly more available as well, but those also never came with they extra memory. ATi's cards had several different versions of the memory upgrade, and often times swapping them off PCI cards didn't work (the connectors were the same but had different pinouts).
Most other brands also had 4MB models, but they were less common. 4MB cards that weren't from ATi almost always used S3 chips. 928, 964 or 968. I am aware of models from Orchid, Hercules, Number Nine, ELSA, SPEA, Miro and Metheus. I suppose one of the Diamond Viper's with the Weitek P9100 also have 4MB models. Matrox had a 4MB model. Then there's that Spider Graphics card that uses the Cirrus Logic CL-GD5434 chip. That's a really odd one, because the integrated RAMDAC wasn't really up to the task of handling resolutions that could benefit from 4MB, plus it uses DRAM (the only one I know of at the moment). I think the S3 864 might have supported 4MB DRAM as well, but I am not aware of any VLB cards that have that combo.
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