> geoff wrote:
> > To: Michael J. Mahon
> > TYhe Second Sight performs various functions, including an Apple II/IIgs
> > video to VGA converter (this is how most Second Sight owners use their
> > card).
>
> > The nice thing about the Second Sight is that if you don't like the RGB
> > display is generated, you can write your software code to make it do
> > something different. You don't have to burn your ROM--just write a
> > driver when the OS boots. Jut because nobody has done this doesn't mean
> > that it doesn't have the capability. It becomes really easy to support
> > enhancements when no hardware changes are needed.
>
> The fact that nobody has done this is a testament to the difference between
> making a thing *possible* and making it *probable*. ;-)
> That this possibility is even discussed sounds like saying "it's
> programmable, so if the designer(s) didn't make it work well, you
> can fix it yourself". ;-)
> > If you want to immediately make HGR look horrible by adding NTSC
> > artifacts, there is nothing to prevent you :)
>
> Actually, I think you would find that the Second Sight doesn't have
> nearly enough processing to provide proper NTSC effects digitally.
> You may be missing some of the context...
> This is part of a protracted and intermittent discussion on how to best and
> most economically provide the capability of connecting an Apple IIgs to a
> modern VGA display--both because of fears of analog RGB monitors failing
> and because of the convenience of being able to share monitors with modern
> machines.
> As with any engineering problem, there are several possible approaches.
> One is to tap into the RGB signals (digital preferred, but analog OK)
> inside the IIgs and, with as little fuss as possible, use them to
> create a VGA RGB stream. A few have had good success with converters using
> "NTSC" scan standards RGB in and providing VGA RGB out. There
> have been experiments using the digital RGB in a similar way, but no
> product yet. (Critical issues are the relation of the sampling clock
> to the Apple dot clock, and the bandwidth of the video processing--not
> too much, not too little.)
> Another method is to eavesdrop on the Apple II peripheral bus and
> completely recreate Apple II/IIgs graphics modes using another
> processor and frame buffer, from which VGA video is generated.
> This has the advantage of extreme versatility, combined with the
> disadvantage of extreme versatility. ;-) It invites the invention
> of graphics modes with no support on the Apple II platforms. To the degree
> that is simply aims to emulate the native Apple II graphics
> modes, it takes on the responsibility of a full emulation--ideally even
> including frame buffer timing for "mixed mode" displays--which is quite
> complex and apparently was never fully done...
> If it isn't clear ;-), I think that the latter approach--the one taken
> by the Second Sight card--is a failed strategy.
> There is no value in offering modes that are not supported by any
> meaningful software base or tools. And the job of fully emulating
> native modes is much more subtle than designers first realize.
> Finally, the vast majority of Apple II graphics are not IIgs graphics--
> they are Apple II graphics designed to be viewed on analog composite
> monitors, where the subtleties of color and the pleasant lack of
> detail (that cannot be represented in Apple II video) is an artistic
> match to the designer's intent.
> I certainly wouldn't want to use it for text displays, but there are
> hundreds of hi-res screens that only represent their designer's intent when
> viewed with limited color bandwidth, and that look positively gruesome in
> standard RGB modes (think dithering). So any VGA converter should offer
> the *option* of processing the video with NTSC artifacts.
> Not offering this option would mean that I would need another monitor
> on my desk just to view these graphics properly.
> Put another way, Woz designed the Apple II to make color on the
> rather imperfect analog NTSC monitors of the day, and legions of
> game designers designed their graphics for these monitors, since
> they knew that practically all of their customers would be using
> similar monitors to view them.
> > Geoff
>
> > > Dave Althoff, Jr. wrote:
> > > > Ferdinan Meyer-hermann
> > > > <ferdinan.meyer-hermann@a2central.com.remove-rw3-this> wrote: : >
> > > > Why did you not add support for the IIGS?
> > > > : So you'll have to wait until someone designs a "GS2VGA"...
> > > > : A real GS2VGA would also have the advantage of being cheaper and
> > > > drawing less : power than a combined solution. And it is likely to
> > > > cause less trouble
> > >
> > > > Anybody remember the Second Sight board? 8-)
> > >
> > > That's not a IIgs video to VGA converter.
> >
> > > The Second Sight was a much more problematic "VGA card for the IIgs"
> > > with the consequent need to support new graphics modes, as opposed
> > > to simply converting IIgs RGB video into VGA video.
> >
> > > The trickiest part of such a conversion would be a mode to handle
> > > NTSC-like color rendition (instead of the much higher bandwidth and,
> > > for many graphics, less attractive "digital RGB" modes) for Apple II
> > > video.