Comment by ajenner

As trollbridge said, there isn't enough VRAM in the CGA to have 200 rows of 80 columns (2 bytes per cell - one for character and one for attribute). But it can be done in 40-column mode. As the CRTC can only do 128 rows unattended, it requires the CPU to be involved (reprogramming the CRTC several times per frame on particular scanlines) but 8088 MPH and Area 5150 did such things.