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Retrocomputing

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    When writing 6502 code for the Atari 2600, I defined macros "sbne", "sbcc", etc. which would squawk if the the target wasn't in the same 256-byte page as the byte following the instruction, since branches across page boundaries incur a one-cycle penalty. In a lot of 2600 code, an extra cycle can cause object locations or updates to be 3 pixels off, cause everything below the current screen location to get shifted down a line, or cause various other bad things to happen. I don't explicitly force loop locations in most cases, but make sure that nothing crosses a boundary. Commented Nov 1, 2016 at 23:45