I found this document relevant to the design of computers with passive graphics output. I hope it will help people with their designs.



Original here.

That ADV478 appnote is a nice find.

The 1992 Analog Audio Video Reference manual has the ADV478 datasheet on PDF page 538, section 6-19.

Related thread: Are there any RAMDACs still being sold?

What I'm seeing here is that the DAC chips comprises different elements in a single unit. If you have seen Ben Eater's worst video card video, you will see that he builds the circuit in two steps: first generating the sync pulses by using counters, and second, using a hand crafted R-2R resistor ladder to do a basic digital to analog conversion.

The thing is that there are companies manufacturing R-2R ladders as chips or other formats. I have to do more research on this, to see which part would be the right one to act as a six or eight bits resistor ladder. And also if the counters could be replaced by a 6502 running in parallel only for generating the sync pulses, sort of like they do it for sound generation.