So, people, this got me thinking. Sorry if this is entirely the wrong place for this post. If so, any pointers welcome.
Anyhow, since it apparently is so easy (hardware wise, anyway) to make a VGA666 GPIO output from the Raspberry, can this approach be tweaked to do:
15 kHz RGB output? This way, Raspberry Pi could drive arcade and TV monitors for faithful emulation of old video games but with greater color separation than you get from the built in composite output.
2) SVIDEO output. https://en.wikipedia.org/wiki/S-Video
3) Composite video. At first glance, this may seem pointless, but AFAIK the built in composite output can not do progressive PAL/NTSC output, just interlace. https://en.wikipedia.org/wiki/Composite_video
4) Drive the deflectors on an old black and white monitor/TV (X & Y) and video intensity directly? (OK - this is pretty far out.)