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40 lines
1.3 KiB
Plaintext
40 lines
1.3 KiB
Plaintext
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KFEST18 SUPER RASTEBAR DEMO
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by deater (Vince Weaver) vince@deater.net
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Written for the Kansasfest Hackfest.
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I started work on this on the morning of Wed Jul 18th and finished
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early in the AM on Saturday July 21st.
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NOTE: If you run the demo and the sound is scratchy and/or the graphics
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corrupted, reboot until it works. Sometimes the vapor-lock doesn't
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happen like it should and I'm not sure why.
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How it works:
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The Apple II lo-res mode is usually limited to 40x48 mode.
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However, there are two graphics pages that can be flipped
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between with a soft-switch.
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If you switch between page0 and page1 at just the right time
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(every 2 scan lines) you can create a pseudo 40x96 graphics
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mode, using all 15 lo-res colors.
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Of course there's no VBLANK notification or HSCAN interrupts
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on Apple II. So you have to read the "floating bus" to find
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out when a scan line begins, and then count cycles to find
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out where to switch things.
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All the calculations for the raster bar, mockingboard sound,
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and scrolling text are done during the 4550 cycles of VBLANK.
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To save space, only two channels of audio are played.
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Code by: deater (Vince Weaver)
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LZ4 code: qkumba
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Music: Muda Kingdom from Super Mario Land (gameboy) by Hirokazu Tanaka
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transcribed from sheet music by G-Han
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