Re: Compact Flash card project for Apple II / IIGS

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

TheByteBooster wrote:

>alex@frankendata.de (TheByteBooster) wrote in message
>news:<8d1d558c.0409150539.6be8fe2a@posting.google.com>...
>> "Tim Haynes" <timhaynes@no.spam.please.alumni.uwaterloo.ca> wrote in
>message news:<ci7e0s$299$1@rumours.uwaterloo.ca>...
>> > "Bill Garber" <willy46pa@comcast.net> wrote in message
>> > roGdnXJhMab5v9rcRVn-jA@comcast.com">news:roGdnXJhMab5v9rcRVn-jA@comcast.com...
>> > >
>>  ...
>> > >
>> > > I think what people want mostly is a card to take the
>> > > Apple II modes and display them on a VGA monitor. Yes,
>> > > a full-featured VGA card would be nice, but what say we
>> > > get a converter card just to display the Apple screens
>> > > onto the VGA monitor for now. Add a connector so you
>> > > can create a daughtercard later and install the VGA modes
>> > > to it at a later time.  :o)
>> > 
>> > I agree.  I think most people would want a SecondSight kind of a card.
>> > Except with DHR support and not being such a power hog.
>> > 
>> 
>> Well this is a completly different beast. Such a converter would have
>> no "inteligence" and be rather "simple" to implement. Such a thing in
>> fact would have not much in common what I think of a graphic card but
>> rather be an interface/converter at best.
>> 
>> Actually I think the SecondSight is all any Apple II users would
>> need... Is it no longer manufactured ?!
>> 
>
>If the only purpose is to convert the IIGS output to hook up a
>standard VGA device why not use: http://www.svideo.com/video2vga.html
>?
>it is listed at $74.95

This is the kind of converter that produces poor results (and I speak
as someone who has a similar converter) for two reasons:

1) it accepts only the composite video, not the higher bandwidth RGB
2) its A/D conversion is not synchronized to the Apple II dot clock, so
   thin vertical lines will "jitter" back and forth as the clock phase varies.

The latter problem would remain a problem even if RGB outputs were
used in the conversion for better resolution.

Another, more subjective, reason for dissatisfaction with the resulting
VGA display of Apple video is that we are accustomed to _sharp_
VGA displays, and seeing an NTSC (TV)-resolution picture full screen
on a VGA display looks terribly "out of focus".

You should be immediately suspect when the converter description
begins with this statement:

"Our S-Video (or composite video) to VGA converter allows you to get
VGA quality from your S-Video or composite video sources."

That is simply impossible.  The chrominance and luminance bandwidth
of NTSC composite video is necessarily limited to less than 4MHz, and
the chrominance bandwidth of S-Video is similarly limited.

A "crisp" 80-column display on an Apple II will require better than 10MHz
video bandwidth, and single-pixel-width vertical lines (as in characters)
will be full brightness only if the bandwidth is at least 14MHz.

There has been much discussion and experiment on this topic in the
past, and there still appears to be no reasonably priced solution.  In
other words, this is a (small) market opportunity.  ;-)

-michael

Check out parallel computing for 8-bit Apples on my
Home page:  http://members.aol.com/MJMahon/