I'm trying to understand at a low level how some early computers and game consoles generated a non-standard form of NTSC. The Wikipedia http://en.wikipedia.org/wiki/Low-definition_television says: "Older video game consoles and home computers generated a nonstandard NTSC or PAL signal which sent a single field type which prevented fields from interlacing. This is equivalent to 240p and 288p respectively, and was used due to requiring less resources and producing a progressive and stable signal." Another source says this was true for the "NTSC Atari 2600, Apple II family, Commodore 64, Nintendo Entertainment System, Sega Master System, and the vast majority of games for NTSC Genesis, Super NES, PlayStation, and Nintendo 64." This page http://www.hdretrovision.com/240p/ calls it a "special timing signal" and gives examples of how contemporary flat-panel TVs can misinterpret the old signal. The issue has spawned the creation of dozen of devices to give the retro look on new TVs. - John