1. The number of scan lines, and therefore the frame time increases from NTSC to PAL according to the following table:

                   NTSC            PAL
               scan   micro    scan   micro
              lines seconds   lines seconds
      VBLANK     40    2548      48    3085
      KERNAL    192   12228     228   14656
      OVERSCAN   30    1910      36    2314
      FRAME     262   16686     312   20055

2. Sounds will drop a little in pitch (frequency) because of a slower crystal clock. Some sounds may need the AUDF0/AUDF1 touched up.

3. PAL operates at 50 Hz compared to NTSC 60Hz, a 17% reduction. If game play speed is based on frames per second, it will slow down by 17%. This can be disastrous for most skill/action carts. If the NTSC version is designed with 2 byte fractional addition techniques (or anything not based on frames per second) to move objects, then PAL conversion can be as simple as changing the fraction tables, avoiding major surgery on the program.

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