So far I'm pretty satisfied. Let's see how far I can get.
Because it's related to the format-questions, I will post a very first routine-label and add some comments.
I know, you work with BW not for the first day now, so I deserve copse' s post - but at this point each detail seems to be very important, so I better repeat it. With that important first routine, the question is answered if Amiga uses Atari-format everywhere. The answer is NO.
Everywhere it is called, code will differ plotting something to the screen.
There is an interface in the PC-code, but not in the Amiga/Atari-versions.
So, please tell me where we can collect 'cards' like this one:
BW_xy_to_offset
AMIGA: 0D8B0 Atari: normal 216F6, extended 221E0
input parameters: D4.w = x, D5.w = y
output: D0.w
result gives an (screen)offset in bytes
for the Amiga the result is aligned to the next bytemargin:
D0 = (320 * D5 + D4) / 8
for the Atari the result is aligned to the next pixelblock to the left:
D0 = V_SCREEN_BYTES_PER_LINE(160) * y + ((x / 2) & 0xf8)
Note:
Amiga label: bruceuncles' 439-disassembly
Atari: basic offset of program start (version?): 0x14000
This one seems to be the last gamecode-routine.
After it I'd say there's only data left, beginning with Label
'WordsText'.
the upper end:
--------------
The screenbase/framebuffer (1st&2nd screen) locations
are 0x60000 and 0x67D00.
0x7D00 is 32000, so 320x200x16 size.
So probably there's nothing anymore from 0x67D00 + 0x7D00 = 0x6FA00 on.
Now the area before 0x60000:
If you check that line:
00006C lea $0005FFFC.l,sp
you'll see, that the area before the screendata gets used for
the stack.
Watching bruceuncle's listing, there are the labels
lbW058484
lbW05886C
lbW058CF8
The first one is located at the border of the last non-zero-datas
and zero-only-datas. But that doesn't mean that this zone is usable.
When I compare the routine using those labels with the Atari, then
this is in the middle of the action. This looks like a RAM-zone.
Can't say yet how far this goes, and how deep the stack will fall.
But for any modification, I'd go for the space after the screens...