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100 lines
2.9 KiB
Plaintext
100 lines
2.9 KiB
Plaintext
Still Alive for the Apple II
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in roughly 20k
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By Deater (Vince Weaver)
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BACKGROUND
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~~~~~~~~~~
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A few years back I implemented Valve's Portal in Applesoft BASIC.
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At the end it played Still Alive, but in horrible single-channel
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speaker beeps. I always wanted to have this sound better.
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So here is the end result. Still Alive in 6-Channel Mockingboard
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Sound in 80 column with cursor effects. Also in 40 column if
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your display can't handle 80 cols. And if you don't have a
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Mockingboard, then a simpler version using P. Lutus'
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Electric Duet 2-channel audio for the stock speaker.
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Fun fact:
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The letter 'Z' does not appear at all in the lyrics to the song.
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(Noticed when I had to edge comparison for uppercase off by one)
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Challenges:
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+ 6-channel audio. Really its 4-channel (from a MOD file)
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but it actually does load and play audio on all 6 channels.
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+ Fitting it all in 48k (want to avoid disk routines if can)
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+ Printing the ASCII art (naive implementation takes longer than 50Hz)
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The ASCII art is roughly 7k. Thought of decompressing
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on the fly, but the LZ4 code is not re-entrant and
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the music is already decompressing on the fly.
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+ Re-using the Lyrics for both the Mockingboard and Electric Duet
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versions.
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+ Squeezing the compressed image into memory leaving room for
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all the code to be decompressed while leaving enough
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room that DOS still has room to load things. It's
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an *extremely* tight fit.
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+ An odd issue where the 80col display would get corrupted
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if we set HIRES without explicitly setting LORES
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before doing PR#3
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Goal: Binary fits in 16k (16384 bytes)
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note size (bytes)
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--------------------- ------
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initial music player: 2078
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add raw ascii art: 9142
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add 3-channel music+lyrics,then slim a bit: 18787
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initial 40 col support: 18864
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have art loading properly 40col: 18910
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lz4 encode the ascii art: 15529
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revert because lz4 code not re-entrant: 18910
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add 4-channel music (KR4): 20128
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add cursor (a bit distracting): 20162
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feature complete 40 col: 20180
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intial 80 col support: 20191
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80 col cursor: 20344
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strip out some unneeded text printing: 19962
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merge ED and MB code: 24993
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properly select between versions: 25001
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merge the ED and MB lyrics: 22828
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80 column ED, wait for keypress+reboot at end: 22852
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Crazy compression:
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Remove mockingboard detection: 16343
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Memory Map:
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0000: Zero Page
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0100: Stack
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0400: Text Page 0 (AUX 0400: 80 column text)
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2000: HGR Page0
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4000: HGR Page1
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9600: DOS 37.5k
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C000: I/O Space
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D000: ROM
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FFFF: END
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Plan:
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Load compressed 16k image ($4000) at $5900 - $9900
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We use MAXFILES 1 to give us some extra room
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just before DOS
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Decompress ENDING sequence at $1800 - $4000
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(writes background to HGR graphics automatically)
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STILL_ALIVE:
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+ $0800 - $5900
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$2e2d of code
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$2282 of KR4 music *or*
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$0842 of ED music
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+ Sound buffers ($3800, 14k) at $5e00 - $9600
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