actually sent per line in 320 and 640 modes on the GS?
Including the left and right borders, plus the horizontal retrace, the video sends out more than 320 or 640 “dots” before the screen begins scanning the next line. Here’s a quick summary of the Apple II video that’s been used throughout the whole series (assuming 60 Hz video here). It’s a slightly modified NTSC signal, though the differences are small enough for most monitors to accomodate. Everything in the Apple II is derived from a 14.31818 MHz master clock. This runs both the video and the processor/memory subsystems. The cycle time is therefore 69.8 ns. For 640-mode (or 80 cols, or double-hires) the dots are sent out at simply this rate. In 320-mode (40 cols or single-hires) the dots are sent out at half that rate, 7.15909 MHz (one pixel every 139.6 ns). The NTSC standard calls for 227.5 cycles of color reference (3.579545 MHz) per horizontal line, for a horizontal scan rate of 15.734 KHz (3.579545/.2275). The Apple II rounds this up to 228 cycles of 3M, so the horizontal scan rat
