pouët.net

vga scrolling and hardware stuff

category: code [glöplog]
 
i was wondering :
is there any way to scroll a vga screen (either vertically or horizontally) by using hardware acceleration or such possilibty not exists so you have to do it with cpu (via memcpy?)

for eg, in pinball fantasies, did they use some graphic card tricks to scroll the table or is it only by software? when this game comes out only slow cpu existed, and game was running without problems so i was wondering how they do...

i was thinking of a mechanism where you copy more than 64k of screen pixels (that start at 0xA000) and then having the possibility to specify where the card should start to dump the info to vga port (eg : 0xB000 instead of 0xA000). so for scrolling you just have to write a single 16bit value...

also : did any other acceleration (like blitting, moving sprite) exists in vga ?
added on the 2010-07-28 21:29:02 by Tigrou Tigrou
I'm actually pretty sure you could change the (0,0) address w/ the vga registers yeah.

No sprite, no blitting in vga.
added on the 2010-07-28 21:38:07 by _-_-__ _-_-__
Vertical scrolling is easy; you change the VGA start address high/low registers.
added on the 2010-07-28 21:40:22 by trc_wm trc_wm
thx all
added on the 2010-07-28 21:50:21 by Tigrou Tigrou
I'm trying to search, but I don't find the 640x400 mode X with a 320x200 window that I'm near sure existed. It allowed to do scrolling both vertical and horizontal... maybe oldschool people here remember that :P
added on the 2010-07-28 21:58:33 by texel texel
If memory serves me right Allegro supported 320x200 with 640x400 virtual screen (back in the days).

http://alleg.sourceforge.net/
added on the 2010-07-29 00:27:42 by datsua datsua
texel: you are right, i think Mode-X Scrolling is what you are searching (*sigh* the good old times ;-)
added on the 2010-07-29 00:29:26 by RufUsul RufUsul
texel: Yes, it was trivial to do 320x200 unchained which gives a total of 256KB of RAM. You can do that as 640x400, or 320x800, or 1280x200, or whatever. That's exactly what Pinball Fantasies does. No hardware sprites, although for super-slow computers with faster VGA cards you could store "sprite" data in vram and use the latches to copy it around. Not a true blitter, but at least the data doesn't have to pass through the bus.

Why are you asking?
added on the 2010-07-29 04:42:06 by trixter trixter
off topic: what happend to that denthor/asphyxia dude?
Wish I knew. My last email with him was 1995.
added on the 2010-07-29 06:45:02 by trixter trixter

login