Re: RGB monitor compatibility

[spec@vax2.concordia.ca (Mitchell Spector)]

In article ab616@chebucto.ns.ca (Tony Cianfaglione) writes...

>   The Commodore 128 RGB is digital and won't work correctly for the GS
>because the GS monitor has an odd (scanning or refresh) rate (15.5??).

    There is nothing odd about it, it is just NTSC horizontal scanning
frequency (the same as a television set) which is 15.75 kHz. Usually
this applies to all composite, digital RGB and older analog RGB (i.e.
those used by IIgs, Amiga, Atari ST, SuperNintendo) monitors. Modern
VGA and SVGA display use 30 kHz or even a much higher horizontal
scanning frequency, which _cannot_ sync downwards.

    Refresh rates have to do with the vertical scanning frequency of a
display, and have nothing to do with compatibility issues. Of course
higher refreshing is easier on the eyes, 60 Hz (what the AppleColor
RGB is stuck at) produces a flicker if you look at the monitor out of
the corner of your eye. Something in the range of 85 Hz or higher is
much, much nicer, it is almost like staring at a sheet of paper. One
of my brother's friends is so sensitive to this, he pushes his SVGA
display to 101 Hz and still wants more! ;)

    Back on the monitor you mention above, it won't work properly
because it is a digital RGB display (64 color maximum usually)
while the GS requires analog RGB. It would probably function with
the proper cable, but you wouldn't be able to display even a
fraction of the 4096 colors, and what colors you would see, would
be incorrect (as you mention below, you have yellow replacing white).

>The IIc (via a Video 7 adapter) works well with the 128 monitor.  I have
>an old Magnavox RGB which has digital and analog inputs so it could
>accommodate both if the rate was correct which it isn't.  The picture
>comes out a cruddy pale yellow.

    If the Magnavox supports analog RGB, than it will work just fine
with the Apple IIgs. It sounds more like your problem is the pinouts
in the cable are incorrectly wired (either that or the voltage to the
blue color gun has drifted and decreased due to age, causing whites to
turn a pale shade of yellow. I had this happen to two AppleColor RGB
as well as a Samsung SVGA display, but I fixed them both up).

Mitchell Spector
spec@vax2.concordia.ca