Re: VGA to Monitor GS (Was Re: Apple IIGS on a VGA monitor...the hard way?)

[mspector@nyx.nyx.net (Mitchell Spector)]

In article dalloff@freenet.columbus.oh.us (Dave Althoff) writes...
 
>I know that some of the nice XGA monitors out there also switch to a
>higher vertical scan rate...say, 74 Hz rather than 60 Hz.  Of course, for
>our 800x600 display, that means bumping the horizontal scan rate up to
>44.4 kHz.
 
    Actually it's only really early SVGA displays that tend to be limited
to a 60 Hz refresh rate (vertical scanning). The Samsung 14" display I
have from 1990-91 is an example, it is limited to 60 Hz when doing 640x480
and higher. Interestingly, you can push it beyond specs with special PC
software like SciTech Doctor. I was able to get it up to 75 Hz in 640x480
but only for a short time period. The AppleColor RGB has the same 60 Hz
limitation, but I've recently wondered if you couldn't push it to 70 Hz
or somewhere close to that by essentially "overclocking" its vertical
refresh rate. Could this be done in software? I would suspect it would
be more a limitation of the GS's VGC chip than the actual display.
 
    Most modern SVGA displays (any decent one) will do at least 85 Hz
these days. Better ones are capable of even more, up to 120 Hz is not
all that uncommon (my brother currently runs his display at 100 Hz).
 
>I suspect that the high scanning frequencies may also be part of the
>reason that modern computer displays cannot generate the brilliant colors
>that our GS displays can.  The dot pitch is so small that the amount of
>screen devoted to each of the three color pixels is curtailed...less area
>per color pixel (and I am talking about screen pixels, all of which are
>red, green, or blue, not to computer pixels) would tend to yield a more
>muted color...but the trade off is much higher resolution.
 
    Hmm, interesting theory. On the other hand, Sony CRT's (and others
that use the Trinitron technology) give extremely vibrant looking color
and use higher scanning frequencies than the GS display. Of course they
don't use a dot mask (or have what you could describe as a "dot pitch")
but a pin stripe instead. The trade off for nice color though, is the
pin stripe seems to commonly have convergence problems in the corners
of the screen and other minor picture distortions (the screen looks
slightly bent inwards). On larger screens you also have a suspension
wire, sometimes two, going horzontially across, which leaves a faint
line of what looks like "dead" pixels. I wish someone could come out
with a conventional CRT that displays vibrant color without trade offs.
 
Mitchell Spector
spec@vax2.concordia.ca