292 lines
8.3 KiB
Plaintext
292 lines
8.3 KiB
Plaintext
Talbot Fantasy 7
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by Deater (Vince Weaver)
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vince@deater.net
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http://www.deater.net/weave/vmwprod/tfv/
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Background
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~~~~~~~~~~
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What you've always wanted, a poorly done FF7 clone for the Apple II.
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Yes, I'm using the 40x40 15-color Low-resolution graphics mode of
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the Apple II. This means the game could in theory run on the original
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Apple II released in 1977 (if you had been fabulously rich enough to
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populate all 48k of RAM).
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Memory Map
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~~~~~~~~~~
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$00 zero page
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$01 stack
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$02-$03 ??
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$04-$07 lores page 1
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$08-$0b lores page 2
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$0c-$0f background graphics
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$10-$1f ??
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$20-??? code AE-20 = 36.4k
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$AE-$B5 music buffer 2k
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$B6-$BD multiply tables 2k
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$BE-$BF ??
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$C0-$CF I/O
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$D0-$FF ROM
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Mode7 Optimization Notes
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~~~~~~~~~~~~~~~~~~~~~~~~
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Original implementation:
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Multiplying 1.0 * 2.0 = 2.0, took 707 cycles
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Multiplying ff.ff * ff.ff = 0.0, took 761 cycles
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Cycles: flying= 162
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 88,179
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Cycles: mode7= 76,077
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Cycles: lookup_map= 33,920
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Cycles: put_sprite= 2,561
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==================================
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Total = 200,971
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Frame Rate = 4.98 fps
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Update Multiply to use zero page addresses:
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Multiplying 1.0 * 2.0 = 2.0, took 616 cycles
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Multiplying ff.ff * ff.ff = 0.0, took 664 cycles
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Cycles: flying= 162
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 76,561
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Cycles: mode7= 76,077
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Cycles: lookup_map= 33,920
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Cycles: put_sprite= 2,561
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===================================
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Total = 189,353
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Frame Rate = 5.28 fps
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Update to use "fast multiply" w 2kB squares table lookup:
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Multiplying 1.0 * 2.0 = 2.0, took 228 cycles
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Multiplying ff.ff * ff.ff = 0.0, took 272 cycles
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Cycles: flying= 162
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 27,041
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Cycles: mode7= 76,077
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Cycles: lookup_map= 33,920
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Cycles: put_sprite= 2,561
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=================================
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Total = 139,833
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Frame Rate = 7.15 fps
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Update to optimize fast multiply (reusing NUM1H, return results in register)
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Multiplying 1.0 * 2.0 = 2.0, took 234 cycles
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Multiplying ff.ff * ff.ff = 0.0, took 278 cycles
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Cycles: flying= 162
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 24,935
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Cycles: mode7= 73,925
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Cycles: lookup_map= 33,920
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Cycles: put_sprite= 2,561
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=================================
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Total = 135,575
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Frame Rate = 7.38 fps
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Add a cache to lookup_map
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Cycles: flying= 162
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 24,935
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Cycles: mode7= 73,445
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Cycles: lookup_map= 24,649
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Cycles: put_sprite= 2,561
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=================================
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Total = 125,824
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Frame Rate = 7.95 fps
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Don't draw sky every frame
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Cycles: flying= 162
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 24,935
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Cycles: mode7= 69,099
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Cycles: lookup_map= 24,649
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Cycles: put_sprite= 2,561
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=================================
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Total = 121,478
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Frame Rate = 8.23 fps
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Move checking if over water out of critical section
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Cycles: flying= 187
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 24,935
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Cycles: mode7= 54,374
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Cycles: lookup_map= 24,712
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Cycles: put_sprite= 2,561
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=================================
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Total = 106,841
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Frame Rate = 9.36 fps
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Move to 40x40 mode
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Cycles: flying= 187
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 49,613
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Cycles: mode7= 123,701
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Cycles: lookup_map= 48,847
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Cycles: put_sprite= 2,561
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=================================
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Total = 224,981
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Frame Rate = 4.44 fps
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Remove some unnecessary zero page copies in the mode7 code
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Cycles: flying= 187
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 49,613
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Cycles: mode7= 141,269
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Cycles: lookup_map= 21,718
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Cycles: put_sprite= 2,561
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================================
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Total = 215,420
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Frame Rate = 4.64 fps
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A few more minor cleanups in the Y loop
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Cycles: flying= 187
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 49,613
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Cycles: mode7= 140,858
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Cycles: lookup_map= 21,718
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Cycles: put_sprite= 2,561
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===============================
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Total = 215,009
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Frame Rate = 4.65 fps
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Add some self-modifying code to inner loop:
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Cycles: flying= 187
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 49,613
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Cycles: mode7= 131,610
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Cycles: lookup_map= 21,718
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Cycles: put_sprite= 2,561
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================================
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Total = 205,761
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Frame Rate = 4.86 fps
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More self-modifying code, also move SCREEN_X to X register
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Cycles: flying= 187
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 49,613
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Cycles: mode7= 118,034
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Cycles: lookup_map= 22,747
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Cycles: put_sprite= 2,561
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================================
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Total = 193,214
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Frame Rate = 5.18 fps
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Remove unneeded precision in the 8.8 x 8.8 fixed point multiply
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Cycles: flying= 187
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 43,588
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Cycles: mode7= 118,034
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Cycles: lookup_map= 22,747
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Cycles: put_sprite= 2,561
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================================
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Total = 187,189
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Frame Rate = 5.34 fps
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In-line unsigned multiply inside of signed multiply (save 12 cycles)
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Multiplying 1.0 * 2.0 = 2.0, took 198 cycles
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Multiplying ff.ff * ff.ff = 0.0, took 218 cycles
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Cycles: flying= 187
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 40,888
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Cycles: mode7= 118,034
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Cycles: lookup_map= 22,747
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Cycles: put_sprite= 2,561
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================================
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Total = 184,489
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Frame Rate = 5.42 fps
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Have loop counter count down from 40 instead of count up (avoid compare)
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Cycles: flying= 187
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 40,888
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Cycles: mode7= 115,538
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Cycles: lookup_map= 22,747
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Cycles: put_sprite= 2,561
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================================
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Total = 181,993
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Frame Rate = 5.49 fps
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Move spacez updates out of line and also do some self modifying code
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Cycles: flying= 187
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 40,680
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Cycles: mode7= 114,830
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Cycles: lookup_map= 22,747
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Cycles: put_sprite= 2,561
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================================
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Total = 181,077
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Frame Rate = 5.52 fps
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Re-arranged multiply result register to allow more optimization.
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This looks like a pessimization, but it's because the cycle counting code
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had been undercounting and missed a few add routines :(
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Cycles: flying= 187
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 40,680
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Cycles: mode7= 115,150
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Cycles: lookup_map= 22,747
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Cycles: put_sprite= 2,561
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================================
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Total = 181,397
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Frame Rate = 5.51 fps
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Make lookup_map inline. Again it looks like an impressive speedup
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but some of this was fixing the cycle count estimates.
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Cycles: flying= 187
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Cycles: getkey= 46
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Cycles: page_flip= 26
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Cycles: multiply= 40,680
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Cycles: mode7= 111,882
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Cycles: lookup_map= 19,872
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Cycles: put_sprite= 2,561
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================================
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Total = 175,254
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Frame Rate = 5.71 fps
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Each cycle removed from inner X loop saves
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32*40=1280 cycles
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