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From: dca@edison.UUCP
Newsgroups: net.micro.amiga
Subject: Re: Re: interlace mode
Message-ID: <633@edison.UUCP>
Date: Fri, 24-Jan-86 09:27:10 EST
Article-I.D.: edison.633
Posted: Fri Jan 24 09:27:10 1986
Date-Received: Sun, 26-Jan-86 04:42:47 EST
References: <570@amiga.amiga.UUCP> <877@h-sc1.UUCP> <511@well.UUCP>
Organization: General Electric Company, Charlottesville, VA
Lines: 26

> In article <877@h-sc1.UUCP>, breuel@h-sc1.UUCP (thomas breuel) writes:
> > |	The trick is to plot a pixel ON and ABOVE the line where the
> > |pixel is to be placed. This still results in an effective resolution
> > |of 400 lines BUT reduces the flicker to almost zilch. I saw this
> > 
> > Sure, if you use 640x400 as a 640x200 mode, then you won't see
> > any flicker, you won't have any higher resolution either, though,
> > and you'll waste a lot of memory.
> 
>     This isnt 640X200 mode.  You still have 400 (399, actually) vertical
> pixel locations, it's just that each pixel is now 2 lines high instead of
> one.  It's the same sort of thing that a lot of machines (specifically
> Atari 800 and Apple II) did to avoid horizontal color aliasing when using
> a standard NTSC type composite monitor.
>  
Huh? obviously I am missing something here.  It seems to me that by making
each pixel 2 lines high we have just created a screen that will hold only
640x200(virtual) pixels.  I would imagine that the 640x200 essentially does
exactly this, i.e. expands that pixel height.  Therefore it seems to me
that using the 640x400 strictly in this manner is equivalent to using the
640x200 mode except more memory (and cycle stealing) is utilized.  The
advantage I might see to this method is that the screen could use 640x200
equivalent mode for all parts of the screen for which it is unecessary to
have maximum resolution and thus minimize the flicker.

David Albrecht