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Atari coding BBS
Re: HBL on Falcon (follow up)
Posted by: Orion Apr,16.2019-12:20 

Regarding the default XBIOS settings, I don't have the VIDEL registers values (I need to dump them).

But for the RGB50 and VGA50, you can find these values here:

Regarding borders, it is almost absent in VGA regardless of the configuration (XBIOS or custom).

As you mentioned, borders are present in the default XBIOS RGB config whereas they are almost absent with the custom RGB50 config.

So for the RGB mode, what you suggest makes senses (and it is coherent with what I observed).

But for the VGA mode, it is not the case: there is no (visible) borders in all configs but despite this similarity the HBL interrupt is triggered in different ways.
Indeed I can see the background color changed:
- one horizontal line earlier with the XBIOS config
- at the expected line, but few cycles late, with the VGA50 or VGA60 configs (without CPU cache)

One additional remark: Evil mentioned the fact that the color must be changed as quickly as possible, typically by the first instruction of the interrupt routine (which is what I do).
But this approach does not work with the default XBIOS settings (ST low rez).

As I mentioned, with the XBIOS configs (RGB or VGA), the timer-B HBL interrupt is triggered too early for that.
And this is why Klaz uses his trick to wait for the expected raster line before changing the color.

So it is unclear to me which display configuration is compatible with Evil's recommendation.
My own experimentation showed that his approach only works with the RGB50 config (ST low rez).

-- Orion

[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

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