On this youtube demo (which might not be real) : https://www.youtube.com/watch?v=ktUguF1TnJk
... I saw this post:

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I remember back in around 1982 or so David Dixon (from Vancouver, BC, Canada) wrote a high-res demo on the Pet by switching characters on the fly as the raster beam was still drawing them. He had worked out all of the combinations of characters needed to turn on each pixel and then it generated self modifying code to make it all run fast enough.
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Can anyone help me locate that demo?
It sounds like something really interesting!