This is the driver that I found at www.diamondlegacy.com/products/drivers/driver-index.htm, it is for the OPTi 82C929A, it should be backwards compatible with your 928 Card.
The card type was not listed on that URL, but it has several other cards using the same chip, so if this one don't work , try surfing the link I gave you might find one that works.
I did see a 924 and a 931 series card listed with not much in between.
I have the books on the 929 series, it shows a Micron Computer, Indicating that Micron may have used these cards in there systems in which case they might also have some drivers for it.
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