Once the VGA standard was introduced, there was a proliferation of 16-bit ISA cards that support VGA along with the previous EGA, CGA standards. There also see

Once the VGA standard was introduced, there was a proliferation of 16-bit ISA cards that support VGA along with the previous EGA, CGA standards. There also seemed to be few obstacles to supporting VGA in an 8-bit card, and if we can believe a few eBay searches, these can still be obtained. So any pre-16-bit XT-bus PC was a candidate for a VGA upgrade. That's how we rolled in those days and that's why building PCs is known as "LEGO for Adults".