and a rare Motorola SC02SH007DK04 graphics chip. As far as I know, no datasheet or detailed documentation for that chip has survived, so its exact features are still unknown

The "SC" prefix indicates a custom chip that Motorola made for someone else - in this case Compaq. A quick search of the Internet shows that it's an SVGA-class card with a blitter and hardware cursor. Here's some register-level docs:

https://flint.cs.yale.edu/cs422/readings/hardware/vgadoc/COM...