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The horizontal beam position has a value of $0 to $E2. The least
significant bit is not used in the comparison, so there are 113 positions
available for Copper operations. This corresponds to 4 pixels in low
resolution and 8 pixels in high resolution. Horizontal blanking falls in
the range of $0F to $35. The standard screen (320 pixels wide) has an
unused horizontal portion of $04 to $47 (during which only the background
color is displayed).

All lines are not the same length in NTSC. Every other line is a long line
(228  color clocks , 0-$E3), with the others being 227  color clocks 
long. In PAL, they are all 227 long. The display sees all these lines as
227 1/2  color clocks  long, while the Copper sees alternating long and
short lines.

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