Frank Linde has developed a HiRes card for the CBM 8296-D. The features of the High Resolution Extension (HRE) are: Resolution of 640 x 250 pixels. The CBM video signal and the HRE video signal can be mixed. Control of the HRE through the User Port (POKE). Integration of simple drawing tasks (GPU). You can read all the details on his blog.

YouTube: High Resolution Extension