What you will do with it? Some quick search:

Mach32/Mach64/RagePro/Rage128 docs and mach64sdk.
http://www.bitsavers.org/components/ati/
https://www.xfree86.org/3.3.6/Mach641.html
https://www.ardent-tool.com/video/ATI_Chip_Markings.html

marxveix wrote on 2025-12-10, 18:36:

What you will do with it?

Writing a driver. For a non x86 system where one cannot use the video BIOS and has to program everything on register level.

Which of the links you provided does provide actual documentation (on register level) for that DAC?

mxmxmx2 wrote on 2025-12-10, 20:22:

marxveix wrote on 2025-12-10, 18:36:

What you will do with it?

Writing a driver. For a non x86 system where one cannot use the video BIOS and has to program everything on register level.

Which of the links you provided does provide actual documentation (on register level) for that DAC?

You have to look, but there are more information in these documents files than your single link, mach32 also has this dac.

None of the ATI docs at bitsavers seems to contain a detailed description of the ATI-68860 DAC. The Mach32 Programmer's Guide has a code snippet that programs a "magic" value, so does the old XFree86 source code. I guess I'll have to do the same. Though I still would prefer to know what I'm actually programming into the registers. Hence, any documentation (data sheet etc.) for that DAC is still highly appreciated.

It was not sold to 3rd parties I think, so documentation just doesn't exist. You can experiment with those magic values and see what results are produced as you change bits in them. Much of it should behave like a normal VGA RAMDAC with only some extra features in new addresses etc. It should only be a matter of couple bits to change data format + color depth related options.