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0 pointsLoSboccacc5y ago0 comments

something I always wondered since the age of programming mode 13h, is the use of the fourth quadrant so that loop would fill video memory in the order the scan line goes reading it?

0 comments

toast05y ago

This is pretty much it. Scan lines are numbered from the top down, as they happen, everything else is numbered accordingly.

The real question is why scan top down and not bottom up? (I don't have any idea). Horizontal scan lines makes sense given a wider than tall screen, because it results in fewer scan lines, lowering the frequencies required ( a bit). Wider than tall makes sense for TV given common movie film aspect ratios and computer monitors started as TVs with different control circuits and cases.

klodolph5y ago

I think it’s just designed to match the English order for text. This way your text mode can go through memory linearly. Graphics mode can just reuse the same order.

j / k navigate · click thread line to collapse

0 pointsLoSboccacc5y ago0 comments

something I always wondered since the age of programming mode 13h, is the use of the fourth quadrant so that loop would fill video memory in the order the scan line goes reading it?

0 comments

toast05y ago

This is pretty much it. Scan lines are numbered from the top down, as they happen, everything else is numbered accordingly.

klodolph5y ago

I think it’s just designed to match the English order for text. This way your text mode can go through memory linearly. Graphics mode can just reuse the same order.

j / k navigate · click thread line to collapse