Reply 1660 of 2062, by TheGreatCodeholio
It would be nice if MDA mode also emulates that MDA only has 4k of video memory (as opposed to the 32k/64k of Hercules).
MDA memory wraps that 4k around in the range of B0000-B7FFF, where Hercules has a full 32k there without wraparound, and another optional 32k from B8000-BFFFF when no CGA card is installed.
It already does. According to the current implementation, machine=hercules already limits memory to 4KB unless a bit is flipped to enable the rest of the memory. machine=mda prevents setting that bit, therefore 4KB limit.