I’ve been looking at the ACV-1030 color card and the Yamaha V6355D chip it uses. At first glance it looks like a normal CGA-style adapter, but it turns out to have a hidden 160x200x16 graphics mode that is much more interesting than the stock card would suggest.

This is the same V6355D family used by the Olivetti PC1, and it has the same kind of hidden graphics capability. The interesting part is that the card can do more than typical CGA output, especially on the composite side where the programmable palette is visible.

I’ve put together a small programming guide and some DOS demo software around it, and I also ported the BMP viewer idea to the ACV-1030 as ACV-BMP. I also added a /CGA option so the viewer can be used in fixed CGA-like output mode.

The reason this is interesting is that it gives a V6355D-based graphics mode in a 286-era system, and it is a fun little retro hardware project. The really nice part is that it gives access to 16 colors selected from a 512-color palette, which is a lot more interesting than plain CGA. For a 286 or 386, most people would still rather use a VGA card, but as a retro hardware experiment it is a very nice little project.

The big limitation is the output path. Composite works for testing and experimentation, but it is not a great display signal. It is good enough to make the hidden mode visible and useful for testing, but not good enough for a serious long-term graphics target. Without a better RGB or TTL-style output path, I probably won’t spend a lot of time porting more PC1 apps and games, or my Sierra AGI and SCI0 work, to the ACV-1030.

So this is mostly a fun retro project right now: a weird little card with a very interesting V6355D graphics mode, some working DOS demos, and some useful reverse-engineering notes. If anyone has ideas for getting a cleaner RGB signal out of the card, I’d be very interested to hear about it.

Links:
https://github.com/RetroErik/acv-1030-v6355-p … ogramming-guide
https://github.com/RetroErik/PC1-BMP