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Retrocomputing

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    The Atari 2600 relied upon software to output a vertical sync pulse every 262-ish lines; many games happen to output 263 or (somewhat less commonly) 261, Stella's Stocking uses 264 because audio is designed around a four-scan-line "loop", and some games end up gaining or losing a scan line here or there based upon object positions. Some older televisions might have needed to have the vertical hold knob adjusted if a player went from a game that happened to output 256 lines to one that output 268, but otherwise television sets were pretty flexible. Commented Jan 28 at 0:12
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    Actually, on the 2600 one of the reasons for games--especially PAL ports--to go beyond 262 scan lines was to increase usable screen real estate. If the worst-case execution time for game logic was 5300 cycles (the 2600 executes exactly 76 cycles per scan line), pushing the screen timing out to 270 lines/frame would allow a game to show 200 lines of meaningful content. Staying within the standard 262-line frame would require limiting content to 192 lines. Commented Jan 28 at 1:02
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    It's OK to not be aware of every computer in existence. The computer I had produced a signal with 320 of 15kHz lines per frame versus expected 312.5 per field of interlaced video. This is 48,828125 instead of 50 Hz, which indeed caused a little beating of image on my portable B/W TV with transformer power supply. Save all-white screen causing the upper half of the raster to dance (due to combination of poor high voltage regulation and wrong v-sync shape, I believe), it worked just fine. Big color TV set didn't have problems with that signal at all. Commented Jan 28 at 6:03
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    To jump in, see digitpress.com/library/techdocs/vcs_scanlines.htm for a list of the number of scan lines various different real Atari 2600 games really pushed as a guide to the tolerances that commercial companies seemed happy with back then. Summary: "For known NTSC games you can find values from 248 to 286, and for PAL from 284 to 342." Commented Feb 13 at 4:49
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    > Computer monitors were often a different beast Until multi-sync monitors became popular, most computer monitors (and arcade cabinet monitors) were basically 15 khz television CRTs without the tuner. Commented May 8 at 0:20