My Z280 now has a 1MB Trident SVGA card. Photo of hardware: http://www.hyakushiki.net/misc/z-svga1.jpg Photo of amazing monitor test pattern: http://www.hyakushiki.net/misc/z-svga2.jpg
Getting that to work was harder than I expected. I had first tried a CL-GD5x0 VGA card, then briefly a CHIPS 82C43x EGA card (though this was wildly impractical due to being a full length card), then the Trident 8900D card, and finally a Western Digital 90C00 VGA card. Then I found the datasheet for the TKD8001 DAC and decided to try the Trident card again. At best I had been getting some nice hsync/vsync signals and a blank screen showing color 0, despite being able to read and write the video memory at $A0000. It turns out the key thing I had missed (and finally ran across in the WD90C00 manual on bitsavers) was bit 5 in $3C0. This register looked like it was just a place where you write your index to access some other register. But if you do that, and don't go back and set bit 5 when you're done, you get a blank screen. Huh.
Getting that to work was harder than I expected. I had first tried a CL-GD5x0 VGA card, then briefly a CHIPS 82C43x EGA card (though this was wildly impractical due to being a full length card), then the Trident 8900D card, and finally a Western Digital 90C00 VGA card. Then I found the datasheet for the TKD8001 DAC and decided to try the Trident card again. At best I had been getting some nice hsync/vsync signals and a blank screen showing color 0, despite being able to read and write the video memory at $A0000. It turns out the key thing I had missed (and finally ran across in the WD90C00 manual on bitsavers) was bit 5 in $3C0. This register looked like it was just a place where you write your index to access some other register. But if you do that, and don't go back and set bit 5 when you're done, you get a blank screen. Huh.