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From: breuel@h-sc1.UUCP (thomas breuel)
Newsgroups: net.micro.amiga
Subject: Re: interlace mode
Message-ID: <878@h-sc1.UUCP>
Date: Sun, 19-Jan-86 22:37:55 EST
Article-I.D.: h-sc1.878
Posted: Sun Jan 19 22:37:55 1986
Date-Received: Tue, 21-Jan-86 07:24:45 EST
References: <570@amiga.amiga.UUCP> <877@h-sc1.UUCP> <511@well.UUCP>
Organization: Harvard Univ. Science Center
Lines: 45

|||	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.

This may do the trick for certain kinds of graphics. For a high-resolution
text display, it may make your characters look nicer, but it does not
allow you to display significantly more characters on the screen.

|  The necessary fix would be fairly expensive. The biggest reason for the
|640 X 200 limitation on each field is to reduce the bandwidth requirements
|of the coprocessor and the memory, and to allow the CPU more cycles. 
|Maintaining the current hardware capabilities and adding the extra capability
|you describe isn't an easy job. (Before I hear anything about the Atari ST
|and its 640X400, 70Hz screen, let me remind you that that is a one-bit-per-
|pixel monochrome screen.  It's ONLY color option is 320X200.  If you are
|willing to accept THAT limitation, then the problem isn't too hard.  If you
|want a color screen such as the Amiga's, at a reasonable cost, compromises
|have to be made.)

Yes, that is precisely the point. For word processing and program development
I vastly prefer high monochrome resolution to low colour resolution. That
is not a bad limitation, it is a reasonable compromise (between cost
and performance). What counts for those applications is whether you can
display one, two, or four usable windows on the screen at the same time,
not whether your menu bar is green and your pop-up menus are pink.

I guess we just have different applications in mind. For my purposes,
a machine with true 640x400 monochrome resolution is just superior to
one with 640x200 colour resolution because I can display more text
on the screen at the same time. Since I otherwise like the AMIGA,
I really regret that it doesn't have this capability. It is unfortunate
to hear that Commodore/AMIGA seems to have no intention of adding
a high-resolution monochrome mode.

							Thomas.