Video Scanner Question

[BryanParkoff@yahoo.com (Bryan Parkoff)]

.....I know that Apple II, II+, //e and //c use Video Scanner that it
starts from $7D00 through $FFFF.  When it reaches $FFFF, it wraps back
to $7D00 because it is only 17030 cycles.  It may make you think that
it increments $7D00, 7D01, 7D02, 7D03, ETC.  No, it does not.  It only
increments $7D00, $7D40, $7D41, $7D42, $7D43 through $7D7F.  It does
the same for $7D80, $7DC0, $7DC1, $7DC2, $7DC3 through $7DFF.  It is
because 7th bit should be set to one after preset is executed during
horizontial blanking.
.....It goes for text, low res, high res and double res.  My question
is how do Apple IIgs handle Video Scanner that support 320x200
resolution and 640x200 resolution.  It can mean that Video Scanner
must be changed to support two super high resolution.
.....Where do I get more information that it is not found in Apple
IIgs Technical Reference and other books, but it is only found in
"Understanding Apple //e" manual.
.....I would appreciate when you have found the information or you
have your own knowledge.  I would love to see more than 17030 cycles
that Apple IIgs handle for video manipulation.  Thanks...

Bryan Parkoff