400 scanline modes gave us 50 lines of text by virtue of loading the 8x8 pixel font (400/8=50). There was no incompatible trickery going on for 43 line mode. Th

400 scanline modes gave us 50 lines of text by virtue of loading the 8x8 pixel font (400/8=50). There was no incompatible trickery going on for 43 line mode. That was just the 8x8 pixel font at the standard 350 scanlines (350/8=43.75). The palette was weird because changing palette entries away from the standard 16 CGA colours was impossible in 200 scanline modes. It was only possible in 350 scanline mode (and also on VGA, but I digress). That's because the EGA could connect (and often would be connected) to CGA monitors and adjusted the pinout of the connector accordingly. This meant just 1 bit per colour channel and 1 intensity bit. The full EGA palette required 2 bits per colour channel and could only be used on actual EGA monitors. The way IBM ensured that was limiting palette changes to the 640x350 mode.