Re: IIgs RGB Port (was More Questions from a New IIgs User)

[supertimer@aol.com (Supertimer)]

jonINTERNETrelayCHAT@napaVALLEYnet.CLARInet (Jon Bettencourt) wrote:

>As you can tell from the subject line, this used to be a post called More
>Questions from a New IIgs User. The mouse and game port question appears
>to be solved, and I think I figured out the AppleTalk thing.
>
>Now, only one question remains: the RGB port.
>
>So far, I've figured out that it outputs analog RGB and has a frequncy of
>15kHz. The Macintosh monitors only work as low as 30kHz, so the RGB
>signals are doubled up inside the monitor.
>
>I tried with the Apple Performa Display. It is distorted and makes a high
>pitched sound. I knew it wouldn't work, just like I knew BLOADing a
>Windows BMP file into HiRes graphics wouldn't work.
>
>I also have an AcerView UVGA monitor hooked up to my PC. Would this
>monitor work? If I had the pinouts of the cable from that monitor, I could
>try it. But I need the pinouts for VGA. I already have a pinout for RGB.

It would not work without extra hardware.  You can use one of
those VGA to Mac adapters to rearrange the pinouts to the
type the IIGS and Mac uses, but you'd end up with the same
distorted image.

http://www.sequential.com/ Sequential Systems sells one type
of solution.  It is an SVGA card for the IIGS.  Naturally, you
plug an SVGA monitor into that card.  The card is called the
Second Sight.

>In the New Questions thread I mentioned doubling the frequency of the RGB
>port. Could I do this easily? Would I need to double something else, like
>the RGB signals? I know I can ("know I can," _not_ "know how I can," by
>the way) modify the _monitor_ to support 15kHz, but I've never opened up a
>monitor before and I don't want to touch the wrong terminal and shock
>myself. Trying to modify the IIgs would be safer.

This is very true.  There are lethal voltages inside monitors and
televisions.  You can modify the IIGS to output a 30Khz signal,
but that would take a Second Sight SVGA card.

>Is there a little thing anywhere that you can put between the cables that
>would double the frequency for me? Would doubling the frequency even work?

This is possible too.  Made for the Amiga, there are devices that
are called scan doublers.  They sit between the Amiga and a
VGA monitor.  The Amiga 1000, for example, uses a 15Khz
signal, just like the IIGS.  The scan doubler doubles each line
and changes the 15Khz signal into a 30Khz one, which then is
then sent to the VGA monitor.  It works well for the Amiga.  It
should work just as well for the IIGS.  However, you would have
to find out the Amiga RGB pinouts and wire your own cable for
the IIGS.