Re:Side Border Bitmap Scroller on the C64
by mdp2021 on Monday December 05, 2022 @04:20PM
(#33872086)
It is not a matter of quantity of memory. (One screen worth of content is just 1000 bytes - 40x25 chars)
Do not forget that the physical pixels sit on real rasterbars on a cathodic ray tube machine.
If you made the centered content bigger, first of all the effect would simply be ugly - stretched;
if you expanded the content per bar (over the 40ch, 320px) but keep the same ratio, you'd have less warranties that the set would make it visible;
similarly for using more rasterbars than 200 (taking into account that compatibility with NTSC basically imposes a limit at 240): will every set display all the lines or cause frustrated users?
(And of course, given the shape of the screen, if you filled it up with a rectangular matrix you would surely lose displaying the content at the corners.)
As others said in a different way: there was a safe area.
Do not forget that the physical pixels sit on real rasterbars on a cathodic ray tube machine.
If you made the centered content bigger, first of all the effect would simply be ugly - stretched;
if you expanded the content per bar (over the 40ch, 320px) but keep the same ratio, you'd have less warranties that the set would make it visible;
similarly for using more rasterbars than 200 (taking into account that compatibility with NTSC basically imposes a limit at 240): will every set display all the lines or cause frustrated users?
(And of course, given the shape of the screen, if you filled it up with a rectangular matrix you would surely lose displaying the content at the corners.)
As others said in a different way: there was a safe area.