Let's break this down in what you should be investigating.
Now the Mega Drive uses the Control Port to write or read to the CRAM (Colors), VRAM (Video), or VSRAM (Scrolling Video). More details here: https://segaretro.org/Sega_Mega_Drive/VDP_general_usage#Control_port
The layout is a bit crazy, but if you can figure out what address the palettes or graphics are being transferred, you could search for address value in a trace.
For example, to write to CRAM address $0: #$C0000000
While the palettes are most likely not compressed, the graphics probably are. There are loads of graphic hacks of SOR2, so I suspect its using a common compression like Nemesis (https://segaretro.org/Nemesis_compression
). Nemesis does have a tool that can detect and separate them, so you could give that a shot.
Now the next thing to figure out is are the tiles being stored in the Plane or as Sprites?
If it's on a Plane, then you have to use Plane Tables to transfer 8x8 tiles to the required location. More details on here: http://md.railgun.works/index.php/VDP#Nametables
If it's using Sprites, then you have to use Sprite Attribute Tables to determine the size, tiles to use, flip, pattern etc. More details here: http://md.railgun.works/index.php/VDP#Sprites
If you can figure the where the address are, you could search the data in the rom, or find it in a trace.
When I get some time, I'll have a look myself. Hope this helps.
August 10, 2019, 07:12:14 am - (Auto Merged - Double Posts are not allowed before 7 days.)
Using the USA version, the title is stored in the Plane B area. The rom stores them as mapping values.English Title (US version) = 38B94 to 38FD4 (440 Hex Bytes)
I also found this in the trace:
00:5C2C 4D F9 LEA ($00038B94),A6
00:5C32 2A 3C MOVE.L #$61060003,D5
00:5C38 7E 21 MOVEQ #$21,D7
00:5C3A 7C 10 MOVEQ #$10,D6
00:5C3C 4E B9 JSR ($000017D0)
5C2C = Offset to Plane Table Title, so you can store the data at end of the ROM and expand.
5C39 = Length of Title (hex)
5C3B = Height of Title (hex)
5C34 = Y Position of Title (hex)
5C35 = X Position of Title (hex)
Now we just need to figure out where the palettes and graphics are. The graphics are not Nemesis compressed, so I need to do some digging. It feels great when you make progress.