I used to program demos for the C64 back in my teens. A lot of the learning was simply reverse engineering the code from other demos, sometimes verbatim copying snippets, always trying to understand. At age 16 I was pretty confident that I had achieved the skille level of a wizard but in reality my understanding was pretty sketchy.
An example: Rendering graphics (i.e. sprites) at the far horizontal edges of the screen would require the CPU to perform some shenanigans to trick the video circuits; this would need to be done on every scanline and required the timing of the CPU to be in close sync with the video hardware. I understood that. I had also experienced how sprites and every eight scanline (aka "badline") would mess up the carefully planned timings. Eventually, I kinda understood that concept. I had also seen, from code that I copied, how triggering a badline could be used to force the CPU in sync with the raster beam but it was akin to black magic for me. Wasn't until years later, programming on the Amiga, that the penny dropped for me.
And of course, grasping the concept and implications of DMA was pretty basic stuff compared to what's going on in this article. I don't think that I'll ever devote the time to understand it in detail but I find it fascinating how people keep discovering new unintended features in the old C64 architecture.
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I used to program demos for the C64 back in my teens. A lot of the learning was simply reverse engineering the code from other demos, sometimes verbatim copying snippets, always trying to understand. At age 16 I was pretty confident that I had achieved the skille level of a wizard but in reality my understanding was pretty sketchy.
An example: Rendering graphics (i.e. sprites) at the far horizontal edges of the screen would require the CPU to perform some shenanigans to trick the video circuits; this would need to be done on every scanline and required the timing of the CPU to be in close sync with the video hardware. I understood that. I had also experienced how sprites and every eight scanline (aka "badline") would mess up the carefully planned timings. Eventually, I kinda understood that concept. I had also seen, from code that I copied, how triggering a badline could be used to force the CPU in sync with the raster beam but it was akin to black magic for me. Wasn't until years later, programming on the Amiga, that the penny dropped for me.
And of course, grasping the concept and implications of DMA was pretty basic stuff compared to what's going on in this article. I don't think that I'll ever devote the time to understand it in detail but I find it fascinating how people keep discovering new unintended features in the old C64 architecture.