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Atari coding BBS
 
Re: HBL on Falcon (follow up)
Posted by: evil Apr,15.2019-11:46 

There are two additional things that havn't been mentioned that limits rasters on Falcon in general and VGA in particular.


1. VGA have twice as fast horizontal frequency, the raster will be further into the screen when the colour is updated

2. Videl have a bug; when you update palette clut, it will generate noise on the screen (at the raster position when you update the colour). The noise can even be seen through bitmap data.


I think if this is going to work well at all, the raster code needs to be quick, eg set the colour first thing in the interrupt. Like wasting an address register for it.

tb:
move.w (a6)+,$ffff8240.w
rte

Or a little slower without register:

tb:
move.w $1c0.w,$ffff8240.w
addq.w #2,-4(pc)
rte


There should be 286 words available at $1c0. Perhaps someone else have a faster method :-)

--
Anders Eriksson
ae@dhs.nu






[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


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