4 ms·

13:21 in the linked video: using the copper to change palette below a certain scanline - that is genius! I really like how creative the 80's and early 90's plat

• 13of40 5y ago
  I think that was also the idea behind the HAM(?) image format, that allowed you to display images with more than 256 colors, by dynamically changing the pallette as the frame is drawn. A similar trick was used to change the location of the screen memory midway through the frame, and that's how they implemented the guru meditation error drop-down. Unfortunately, IIRC, the CPU was so slow the raster would travel about ten pixels between changes, so it was mostly just good for effects that used full scan lines, like raster bars, etc. You couldn't use it to programmatically draw a high resolution image or anything like that.
  • snvzz 5y ago
    >A similar trick was used to change the location of the screen memory midway through the frame, and that's how they implemented the guru meditation error drop-down. A simpler example, the support for showing multiple virtual desktops (Amiga called them screens) at once. The DMA registers in the Agnus and the video mode in Denise would be set to the next screen at a certain point @ raster, triggered by the copper.