Re: Second Sight Card

[Paul Schultz <pschultz@med.wayne.edu>]

On 24 Feb 1998, Mitchell Spector wrote:

> 
>     Well it reads the SHR video data and then shadows it to the Oak
> chip, redrawing the graphics from scratch on either a 640x400 or a
> 640x480 screen. For one things graphics will draw _slowly_ as the
> card is not able to keep up (I recall people saying they could see
> the screens being drawn in the Finder, even with an accelerator!).
> The actual screen being shadowed is still only 640x200 pixels, so 
> I'm not so sure the aspect ratio will be corrected. It will most
> likely look squished or stretched and still _not_ do WYSIWYG.

Mitchell,

The 640x200 SHR video is indeed emulated on a 640x400 VGA mode
screen. However, the aspect ratio is exactly like the original
IIgs 640x200 mode. The SS does an excellent job in this area.

>     If your using an SVGA monitor, there will be no scanlines BUT
> you will get chunky square pixels over the GS's small round ones.
> Also, dithering will become noticable, no longer will colors in
> the 640 mode appear solid (e.g. the Finder backround will appear
> as vertical blue and white stripes, not periwinkle blue). Oh, and
> if you try and run games or anything with lots of animation, many
> frames will skip or things will be choppy.

For the most part, the chunky pixels are really never noticed. I think
the only game I recall seeing them in was Boggled GS. The large font
used is drawn with a more jagged edge to it.

The dithering is no more noticeable than with the original GS modes.
In fact, the periwinkle blue looks excellent.

The animation keeps up extrememly well with Wolf 3D with no loss of
frames or 'choppy' behavior. I really think the SS works better
than you were made to believe. Sure, it isn't a speed demon but it
handles the GS emulation (other than DHR!) pretty well.

> 
>     Yep, it replaces the Apple 40/80 columns text font with the PC
> ANSI font used by the Oak chip. This also means mousetext will be
> replaced by the closest ANSI equivalents (and there are very few
> that match). Generally this is _much_ more readable than the Apple
> font--considering it's larger, better definded, bolder and lacks
> scanlines running horizontally through it. On most monitors, it
> should also refresh at 70 Hz if they're capable (meaning you get
> less flicker and reduced eye strain).

Actually, the SS does display all the MouseText characters
correctly with the PC style text font. Jawaid coded the special
MouseText characters in himself. Also, the text font can be
changed. There was a program written to do this. I can't remember
its name at the moment.

> 
>     Overall it actually degrades the quality of your image: Big
> chunky pixels, several poorly supported or _not unsupported_ at
> all video modes, SLOW drawing to screen, kills dithering effect
> in 640 mode, etc. In the end, your going to want to keep your
> old AppleColor RGB connected along side an SVGA monitor for
> full compatibility 

Actually, I think I've pointed out above that the SS does a very
nice job emulating the GS video modes (except for DHR which just
plain doesn't work with the latest ROM). Any speed problems
come with trying to use the VGA modes for animation. You are
right the OAK chip isn't a speed demon. But, for GS emulation...
it does the job. Dithering is faithfully emulated. The pixels
are only occasionally noticeable as chunky and screen re-draws
are fairly fast (admittedly, I do have a ZipGS at 12.5 MHz).

Overall, the SS does a very nice job emulating the GS video
modes. In fact, if it handled DHR correctly it would be
perfect in the emulation department. Where it has a weakness
is the OAK chips ability to perform animation on the IIgs
in the higher resolution VGA modes. I must admit, another
limitation may well be the menu redraws in IIgs desktop
programs on an unacellerated GS. This may indeed be the
'noticeable redraws' that you have heard about. But, no 
problem here.

Paul.

pschultz@med.wayne.edu
Paul Schultz