Something else the article gets wrong, and this is a nitpick, is that it implies every scanline is redrawn every single time. This is called progressive video, and CRTs didn't do this. CRTs did something called interlaced video, where every <i>other</i> scanline is redrawn in a given screen update: Evens, then odds, then evens, and so on. This was done to reduce bandwidth requirements and to prevent flicker.<p>(Progressive versus interlaced is the difference between the "p" and the "i" in 480p versus 480i, 1080p versus 1080i, and so on.)<p>Therefore, with interlaced video, each screen update, called a "field", only has <i>half</i> of the data of a complete frame, and the other half is not sent: The next field is one-half of the next frame. Therefore, interlacing cannot be undone cleanly. Deinterlacing, and it's called, is inevitably a process of reconstructing an image which has passed through a rather brutally lossy compression algorithm.<p>(Distributing interlaced video where the same frame is broken up into two fields, and therefore frames <i>can</i> be reconstructed cleanly, is called "progressive segmented frame". It was used in film-to-video transfer.)<p><a href="http://www.lurkertech.com/lg/fields/" rel="nofollow">http://www.lurkertech.com/lg/fields/</a>
Oh boy, those were the tough times for chip designers. sprite0 and mapper triggering are clever hacks that could have been avoided with <100 transistors (8 bit counter) in the PPU to let you trigger an interrupt on arbitrary raster.