[HN Gopher] C64: Putting Sprite Multiplexing to Work
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       C64: Putting Sprite Multiplexing to Work
        
       Author : ibobev
       Score  : 63 points
       Date   : 2026-03-02 12:35 UTC (1 days ago)
        
 (HTM) web link (bumbershootsoft.wordpress.com)
 (TXT) w3m dump (bumbershootsoft.wordpress.com)
        
       | kickaha wrote:
       | I have been waiting forty years to learn how to do this.
        
       | boomlinde wrote:
       | You can chain handlers by simply rewriting the interrupt vector.
       | Something like this (for a sequence of two handlers):
       | handler1             ; ...             lda #<handler2
       | sta $fffe             lda #>handler2             sta $ffff
       | lda #line2             sta $d012             rti
       | handler2             ; ...             lda #<handler1
       | sta $fffe             lda #>handler1             sta $ffff
       | lda #line1             sta $d012             rti
       | 
       | To my intuition it seems it would be quicker, though slightly
       | larger.
       | 
       | I've only skimmed through the article so maybe there's a reason
       | the author considered this and opted not to. Running out of
       | memory maybe?
        
         | classichasclass wrote:
         | Nitpick: I think he still has the Kernal banked in, so he'll
         | need to use the soft vector at $0314. But that is exactly how
         | I've done chained raster splits otherwise. It's really the most
         | straightforward approach.
        
         | neonz80 wrote:
         | If you put both handlers in the same 256 byte page you can get
         | away with only updating the low byte of the address.
        
       | schlauerfox wrote:
       | I'm ignorant of most C64 stuff being an Atari kid, but I did find
       | this pretty impressive (it's a cheat) with seemingly 9 sprites at
       | once. https://www.youtube.com/watch?v=Ws4twUyt-MY
        
         | Tuna-Fish wrote:
         | The demo has brilliant pacing. When it starts with the sprites
         | moving in a big circle, initially I'm not impressed at all,
         | because C64 has 8 sprites _per line_ , and changing the sprites
         | to be drawn when the screen is halfway drawn is pretty much the
         | first trick you learn. Then the sprites move to the top of the
         | screen, where they are all on the same line together, and my
         | jaw drops.
        
           | classichasclass wrote:
           | Plus, Linus did it in the border, where _only_ sprites can
           | be, so it can 't be a trick with bitmap graphics or custom
           | characters.
        
             | Fr0styMatt88 wrote:
             | That music too! Dang the SID sounds good.
        
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       (page generated 2026-03-03 23:01 UTC)