dos33fsprogs/demos/megademo

Apple II Cycle Counting Megadmo

Demosplash 2018 1st place Retro Demo

by Vince "deater" Weaver, VMW Productions




Memory Map:
	$0000-$0100 = ZERO PAGE
	$0100-$0200 = STACK
	$0400-$0800 = TEXT/GR PAGE0
	$0800-$0C00 = TEXT/GR PAGE1
	$0C00-$0fff = we use this as TEXT/GR offscreen buffer
	$1000-$1fff = 4k free
	$2000-$3fFF = HGR1 page	; note we never use HGR2 ($4000-$6000)
	$4000-$9600 = roughly 20k(?)
	$9600-$BFFF = DOS3.3
	$C000-$FFFF = peripherals/ROM

	Largest can load from $4000 to $9600 = 22,016
	Largest can load from $1000 to $9600 = 34,304
	$4000-$C000 = 32768


C64:
Apple II:
Starring:
	Three pages page flipping.  Hires colors subset of Lores so
	can replicate a blocky color image.  Could in theory animate this
	at 60Hz.  Also could flip between 4 pages, but need the 8k of
	HGR page2.

	For cycle-counting timing, jmp one into a bit $C055 instruction
	which is EOR $C0,X (4 cycles)

	Note, discover that the LORES and HIRES pages aren't exact matches
	for each other, even when using same color.  Half-pixel off?

E-mail:
	Half screen text, half 40x96 lores.
	Text is also interlaced top/bottom to create new chars (including
	some lowercase) on Apple II+ and before w/o lower case.
	Trouble as the built-in font is offset a frame on II vs IIe?
	Also annoyance, my GR compressor uses Grey2 (color $a) as encoding,
	which means can't use a GR image to hold plain black spaces (char $a0)