Charlie<charlieDOTd@verEYEzon.net> wrote:
On 10/7/2011 5:04 AM, Daniel Kruszyna wrote:
Charlie<charlieDOTd@vereyezon.net> wrote:
The problem is that any device that proposes to generate VGA video from an
Apple II (of any stripe) must also faithfully (instantaneously) render the
results of rapid video mode switching--a very difficult feat for non-native
video generation.
I'm not sure I see the problem. To switch video modes you need only "watch"
for accesses to the appropriate soft-switches. When a soft-switch is
accessed the card switches to the appropriate circuitry, probably faster than
the Apple II. While "playing around" with the Carte Blanche VGA video I
often have two monitors (one with the native Apple video and the other from
the Carte Blanche) side by side and I see no perceptible difference when
video modes are switched. The hardest part (for the designer) is knowing
what happens when certain soft-switch combinations are accessed. The
documentation is a little vague on some modes.
The difficulty arises when soft switches and video ram are changed _while the
screen is being drawn_. In this case, the converter must be synchronized to the
native video scanner.
In the case of the Carte Blanche card the video RAM and soft-switches are
being used in a very similar way to the native Apple. Any problem that
would arise from changes to the video RAM/soft-switches while the screen
is being drawn should be the same for both. The Carte Blanche and
presumably the Second Sight card do not generate the VGA "on the fly" but
buffer the video RAM and internally mimic the status of the
soft-switches. The speed of the card is much faster than the Apple so it
can easily keep the buffer "up to date".
As Alex has pointed out, the GS specific modes are not supported "out of
the box". Still with limitations (mostly with the number of colors) you
can have a very sharp (some would say too sharp :-) Finder Desktop. See
the picture at this link:
http://noboot.com/charlie/cbnotesgs1.htm
Charlie
Are you saying that a SecondSight or Carte Blanche will correctly render an
Apple display in which a "window" of a different video mode (say, hi-res)
is created by synchronous mode switching within a page of a different mode
(say, text)?
That's a pretty tall order...
-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon