Category:6502 Assembly: Difference between revisions
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===Looping Backwards Is Faster=== |
===Looping Backwards Is Faster=== |
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Looping is generally faster if the loop counter goes down rather than up. This is because <code>DEX</code> and <code>DEY</code> set the zero and negative flags if their value is zero or #$80 or greater. Generally speaking, this means that when your loop counter goes down, you don't have to use the <code>CMP</code> command to determine if the end of the loop is reached. |
Looping is generally faster if the loop counter goes down rather than up. This is because <code>DEX</code> and <code>DEY</code> set the zero and negative flags if their value is zero or #$80 or greater. Generally speaking, this means that when your loop counter goes down, you don't have to use the <code>CMP</code> command to determine if the end of the loop is reached. |
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<lang 6502asm> |
<lang 6502asm>LDX #3 ;set loop counter to 3. |
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LDX #3 ;set loop counter to 3. |
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loop: |
loop: |
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;whatever you want to do in a loop goes here |
;whatever you want to do in a loop goes here |
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compared to: |
compared to: |
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<lang 6502asm> |
<lang 6502asm>LDX #0 ;set loop counter to 0. |
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LDX #0 ;set loop counter to 0. |
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loop: |
loop: |
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;whatever you want to do in a loop goes here |
;whatever you want to do in a loop goes here |
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