Re: Create Text & High Resolution into Screen

[mjmahon@aol.com (Michael J. Mahon)]

Bryan Parkoff wrote:

>    You claim that 40 column uses 7 pixels while 80 column uses 14 pixels.
>I would have to disagree because 40 column uses A PAIR OF PIXELS to form 14
>pixels that looks like 7 pixels.  Read below.
>    In fact, both 40 and 80 columns still use 560x192 resolution.  Both GR,
>HGR, and DHGR still use 560x192.  It is true that it makes you to think that
>it is really 280x192.  When you use 40 column, GR and HGR, it always paints
>A PAIR OF PIXELs each pixel.  It is a lot of trick to make us think that
>way.  80 column and DHGR do not use A PAIR OF PIXELs so it uses one pixel
>each pixel.
>    Only NTSC monitors and TV display 560x192, but outside of 560x192 are
>blank or unused.  I have no idea how RGB monitor for Apple IIgs can match
>560x192 to 640x400 for GS/OS.  It makes us puzzled.  How can we recognize
>the blue border around 560x192 before we switch to 640x400.  Didn't the blue
>border stretch little bigger allowing 640x400 to fit?  If 640x400 switch to
>320x200 for GS/OS 40 column.  It may still use A PAIR OF PIXEL each pixel.
>It is unlike VGA monitors that they never use PAIR OF PIXELS.

WRT the 7 vs. 14 pixel question, it's really not important how many times
the same dot is clocked out unchanged.  The number of pixels in a line is
counted as the number of pixels that can be different.  For example, in
normal lo-res mode, there are 40 "blocks" across each horizontal line,
and so the display is effectively 40 lo-res "pixels" wide.

I am not familiar with the IIgs super-hi-res mode, but it is a completely
different mode than the usual Apple II modes.  It is, BTW, 640x200,
not 400--even the IIgs RGB monitor uses non-interlaced, NTSC-like scan
rates.  If the pixel field fits within the same horizontal boundaries as the
280x192 or 560x192 graphics pages, then the dot clock must be faster
by the ratio 640/560.  A faster dot clock would be incompatible with
the Apple's usual way of generating composite color video, but would
pose no problem for an RGB monitor.

-michael

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