Re:How early 8-bit arcade machines differed in design from 8...
by cmrdporcupine on Tuesday October 09, 2018 @03:08PM
(#18178916)
Atari 8-bit could fine scroll horizontal and vertical. In 1979.
https://www.atarimagazines.com/compute/issue67/338_1_Atari_F...
Re:How early 8-bit arcade machines differed in design from 8...
by tinus_hn on Wednesday October 10, 2018 @02:00PM
(#18187369)
Which is the same circular buffer. Great if you can spare the memory, it uses twice as much if you want to scroll in one direction or four times if you want both directions.
On the C64 that’s 8k which is a lot if 16k is all you get (the video chip only has enough address lines to address 16k).
Re:How early 8-bit arcade machines differed in design from 8...
by jacobush on Tuesday October 09, 2018 @01:40PM
(#18178082)
Still, it wasn't like you had to push all the pixels. You only moved 8x8 (or whatever it was) characters. So the C64 was pretty decent, actually. Also, of course you had to shift characters once every 8 pixels.
I was envious as hell on my MSX, which had no pixel shifting at all.
Re:How early 8-bit arcade machines differed in design from 8...
by tinus_hn on Tuesday October 09, 2018 @04:13PM
(#18179433)
It’s very helpful and the implementation is ingenious but not very complicated.
Vertical scrolling changes the timing of the bad lines and horizontal scrolling the timing of the bitmap data fetched and this causes the image to come out at a different position.
There are a lot of creative tricks you can do with this though, especially with vertical scrolling.
On a console you typically have a circular buffer and the screen is a movable window on it, so you only have to paint one row every time.