Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!olivea!mintaka!bloom-beacon!eru!hagbard!sunic!dkuug!daimi!pilgrim
From: pilgrim@daimi.aau.dk (Jakob G}rdsted)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: I got problem with overscan*interlace*PAL
Message-ID: <1991Jun14.010430.20831@daimi.aau.dk>
Date: 14 Jun 91 01:04:30 GMT
References: <1991Jun2.183144.22881@daimi.aau.dk> <1991Jun3.135118.944@csc.canterbury.ac.nz> <1991Jun4.175631.20446@daimi.aau.dk> <3622@wn1.sci.kun.nl>
Sender: pilgrim@daimi.aau.dk (Jakob G}rdsted)
Organization: DAIMI: Computer Science Department, Aarhus University, Denmark
Lines: 53

rhialto@cs.kun.nl (Olaf'Rhialto'Seibert) writes:

>>>In article <1991Jun2.183144.22881@daimi.aau.dk>, pilgrim@daimi.aau.dk (Jakob G}rdsted) writes:
>>>> I use a PAL a500. Both of these programs fail on one type
>>>> of pictures. That is, interlaced, 4colour overscan pictures.
>>>> It seems like, when one tries this, that the machine acts like
>>>> the display is NTSC.

>>And that is the only solution? And whose "fault" is it, i.e. is it
>>a hardware or software bug, is it OS dependant(= fixed in 2.0) ? or
>>what? I'm glad to hear it was not me going mad, it has driven me
>>crazy( :-) for the last 2 years.

>It is a software fault. Comparing different cases, analyzing the copper

Yes, I know that moving the screen sufficiently to the left(below 216)
makes the problem disapper. But why does it go NTSC(?) at


>The relevant factors are
>1. >= 640+32 (= 672) pixels wide (hires)
>2. > 216 lines high (in non-interlace mode)
>3. 4 bitplanes

the conjunction of these factors? It works with 3 bitplanes, but not with
four; I would expect it to be hardware limitations then.  

The reason I am still interested in this is, that I have had to move my
screen much more to the left than previously, to be able to view 16 colour
pictures.
   As a result of this, the horizontal position pin on my monitor had to
be adjusted a lot to the right, to put the picture back on the screen. And
this has given me a rim of light in the right side of the screen; it
seems like turning the screen to the extreme right makes the scan lines
"reflect back" on the screen again(does this make sense?). To avoid it,
I instead have to use smaller overscan screens, and this was not what
I wanted...

   On the same note, I remember having read several places, that overscan
was not "part of the system"/not supported; the effect of this being
that you should only hope for overscan to work, but not rely on it, i.e.
future changes to hardware may or may not support it.  Could anybody
with some knowledge date this information and tell, how "true" this is -
what is the "legal" state of overscan for the time being, as well as for
the future? 



--
From the notorious
                      Jakob Gaardsted, Computer Science Department
Bed og arbejd !            University of Aarhus,  Jylland (!)
(Pray and work!)  AMIGA!  pilgrim@daimi.aau.dk | I'd rather play Moria.