Xorya is capable of showing 640x400 black-and-white images by constantly switching half-frames 640x200 every frame to make "fake" interlaced video and some NTSC TVs will "stitch" those half-frames to full frame thinking it's truly interlaced video - some examples:
The only problem with fake interlaced screen - sometimes TVs may be confused and switch odd and even lines:
To resolve it just re-connect the cable once or twice and it will stay in sync until reset.
And some TVs will just constantly blink (usually cheap ones).
Source code of the program:
Use GIGA define to show 400-line XBM images ( it's a reference to ZX-Spectrum world where this technique was called "gigascreen" ; )
By default this example shows schematics of color Xorya in 640x200 without GIGA :)