If "[Patch] Cirrus_vga: More than 1024 lines" for hw/cirrus_vga.c is used, CRTC
Mode Control (CR17) bit 2 can be set to double the number of scanlines to 2048.
In vgabios-0.6c the 1024x768 modes can simply be transformed into additonal
1024x1536 modes. It is only necessary to set CR17 bit 2. For
Cirrus VGA implementation supports 10 bits to set the number of scanlines which
results in a maximum of 1024 pixel for vertical resolution. For large monitors
(e.g. portrait monitor) it would be nice to have more lines.
According to Cirrus technical documentation in gd5446trm.pdf (can be found e
