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Atari coding BBS
| Re: HBL on Falcon (follow up) |
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Posted by: Orion
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Apr,12.2019-00:30
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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?
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Topic
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Posted by
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Date
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HBL on Falcon (follow up)
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Orion
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Apr,11.2019-18:59
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Re: HBL on Falcon (follow up)
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Orion
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Apr,12.2019-00:30
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Re: HBL on Falcon (follow up)
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mikro
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Apr,12.2019-09:08
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Re: HBL on Falcon (follow up)
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Orion
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Apr,12.2019-11:50
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Re: HBL on Falcon (follow up)
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Daniel
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Apr,15.2019-00:09
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Re: HBL on Falcon (follow up)
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mikro
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Apr,15.2019-11:46
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Re: HBL on Falcon (follow up)
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Orion
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Apr,15.2019-15:12
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Re: HBL on Falcon (follow up)
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evil
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Apr,15.2019-11:46
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Re: HBL on Falcon (follow up)
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Orion
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Apr,15.2019-14:39
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Re: HBL on Falcon (follow up)
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mikro
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Apr,16.2019-07:43
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Re: HBL on Falcon (follow up)
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Orion
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Apr,16.2019-12:20
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Re: HBL on Falcon (follow up)
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Daniel
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Apr,16.2019-23:45
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Re: HBL on Falcon (follow up)
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mikro
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Jun,16.2019-14:26
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Re: HBL on Falcon (follow up)
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mikro
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Aug,30.2019-08:32
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What's the anti-troll code?
That's your personal code to be able to add comments and messages on the dhs.nu site.
Don't have a code or forgot it? Fix it here.
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