Search site Dead Hackers Society
Other BBSes »
 
 

Silly Venture 2019

Sommarhack 2019
Demoscene   º   Coding   º   CT60   º   Buy/sell   º   Misc/crap   º   Alive magazine   º   SNDH/Tracking

Atari coding BBS
 
Re: HBL on Falcon (follow up)
Posted by: Orion Apr,12.2019-00:30 


Here are some more details coming from additional investigations:

1) In RGB mode, the behavior is close to that of the ST, although it is more difficult to "hide" the interrupt jitter.
In particular, in this mode, the Timer-B/HBL is triggered as expected and the ST palette can be changed anywhere in a raster line.

2) In VGA mode, things are totally different.
As far as I understand, there are two mechanisms which impact the Timer-B/HBL behavior and the way color changes are handled:
a) In VGA / ST-Compatible mode, the VIDEL is configured to double lines.
b) With the VIDEL, every raster line is divided into 2 (horizontal) halflines.
The consequences (I observed) are the following:
- the Timer-B/HBL is triggered at the beginning of the second (horizontal) halfline (in other words, in the middle of the screen).
- The palette cannot be changed anywhere in a raster line: when a color is changed while a raster line is displayed, that change may be taken into account or may be ignored.
- It is possible to change colors in the middle of a "doubled" (vertical) raster line.

Is it possible to use VGA in ST-Compatible mode to run ST games or demos which play with the HBL for palette changes or to display rasters?





[All messages in this thread]

Topic Posted by  Date 
HBL on Falcon (follow up) Orion Apr,11.2019-18:59
  Re: HBL on Falcon (follow up) Orion Apr,12.2019-00:30
    Re: HBL on Falcon (follow up) mikro Apr,12.2019-09:08
      Re: HBL on Falcon (follow up) Orion Apr,12.2019-11:50
        Re: HBL on Falcon (follow up) Daniel Apr,15.2019-00:09
          Re: HBL on Falcon (follow up) mikro Apr,15.2019-11:46
            Re: HBL on Falcon (follow up) Orion Apr,15.2019-15:12
        Re: HBL on Falcon (follow up) evil Apr,15.2019-11:46
          Re: HBL on Falcon (follow up) Orion Apr,15.2019-14:39
            Re: HBL on Falcon (follow up) mikro Apr,16.2019-07:43
              Re: HBL on Falcon (follow up) Orion Apr,16.2019-12:20
          Re: HBL on Falcon (follow up) Daniel Apr,16.2019-23:45
            Re: HBL on Falcon (follow up) mikro Jun,16.2019-14:26


Message board and comments are now read-only

Due to abuse of the message boards we have put the entire site in read-only mode. That means you can't post new threads or reply to old messages and you can't add comments in VideoDB and PicDB.

Some messages have been erased from reading, but are stored in case they need to surface again.

After 17 years and 45000 messages we're shutting down due to one person.




© 1994-2019 Dead Hackers Society Contact: Anders Eriksson