base:20-pixel_sprite_interleave
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| Both sides previous revisionPrevious revisionNext revision | Previous revisionNext revisionBoth sides next revision | ||
| base:20-pixel_sprite_interleave [2020-10-15 14:42] – raistlin | base:20-pixel_sprite_interleave [2020-10-15 14:45] – raistlin | ||
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| Line 69: | Line 69: | ||
| </ | </ | ||
| - | What matters to us here is the cycle count between our first write to the sprite values and our last. So that's 7x2 + 7x4 = 42. To reduce this, we can use the illegal opcode, SAX:- | + | What matters to us here is the cycle count between our first write to the sprite values and our last. So that's 7x2 + 7x4 = 42 cycles. To reduce this, we can use the illegal opcode, SAX:- |
| < | < | ||
| LDA #64 + 4 | LDA #64 + 4 | ||
| - | LDX #fb | + | LDX #$fb |
| - | SAX ScreenAddr + $3f8 + 0; <-- SAX will write A&X .. ie. 64 in this case (we mask out bit 2) | + | SAX ScreenAddr + $3f8 + 0; <-- SAX will write "A & X" |
| STA ScreenAddr + $3f8 + 4 | STA ScreenAddr + $3f8 + 4 | ||
| INX | INX | ||