How to use the SSFII mapper

;From a SSFII Doc - credits to Bart Trzynadlowski and Tim Meekins, those who contributed information

;

;The Sega Genesis/MegaDrive maps ROM from 0x000000 to 0x3FFFFF which means that
;the CPU can only see 4 megabytes of cartridge ROM.

;

The SSFII mapper is a special ROM remapper/bankswitcher on the first 4MB ROM space
that is used to break the the classic 4MB limit.

To use the SSFII mapper on Sonic 1, 2, and 3&K,
Copy and paste this macro to the beginning of your asm file.:


setROMBank    macro    page,range        ; page = 0-63 (16MB) 512KB pages useable
                        ; range = $A130F1 = $0-$7FFFF not writable

        if range=$80000
        move.b  #page,($A130F3).l    ; range = $A130F3 = $80000-$FFFFF
        endif
        if range=$100000
        move.b  #page,($A130F5).l    ; range = $A130F5 = $100000-$17FFFF
        endif
        if range=$180000
        move.b  #page,($A130F7).l    ; range = $A130F7 = $180000-$1FFFFF
        endif
        if range=$200000
        move.b  #page,($A130F9).l    ; range = $A130F9 = $200000-$27FFFF
        endif
        if range=$280000
        move.b  #page,($A130FB).l    ; range = $A130FB = $280000-$2FFFFF
        endif
        if range=$300000
        move.b  #page,($A130FD).l    ; range = $A130FD = $300000-$37FFFF
        endif
        if range=$380000
        move.b  #page,($A130FF).l    ; range = $A130FF = $380000-$3FFFFF
        endif
        endm
;From a SSFII Doc - credits to Bart Trzynadlowski and Tim Meekins, those who contributed information

;

;A page is
;specified with 6 bits (bits 7 and 6 are always 0) thus allowing a possible 0-63
;pages (SSFII only has 9, though.)
;
;The first area, 0x000000-0x07FFFF is fixed
;and cannot be remapped because that is where the vector table resides.
;

Remember, the 'range' cannot be none other than:
$80000
$100000
$180000
$200000
$280000
$300000
$380000

Then, copy and paste this under the GameProgram label (or the Test_LockOn label for Sonic 3&K):


;        move.b  #2,($A130F1).l ; SRAM?
        move.b  #1,($A130F3).l
        move.b  #2,($A130F5).l
        move.b  #3,($A130F7).l
        move.b  #4,($A130F9).l
        move.b  #5,($A130FB).l
        move.b  #6,($A130FD).l
        move.b  #7,($A130FF).l
This sets up the first 4MB of the ROM correctly.

Finally, remove the ChecksumCheck routine.

Tested and works on Regen and Kega Fusion.
Hope this helps you all people!
If there is anything missing, reply here.

 

How does this interact with the SRAM handler, if at all? At one point, GerbilSoft said that $A130F1 is involved there if the ROM is >= 2 megabytes.

 

The "CPS1" versions of the Super tracks aren't actually the CPS1 in action - it's still similar stuff, however they're actually from the Sharp X68000 port of SSF2 (and the FM versions of the original tracks in that are far superior to the original CPS1 tracks). Still, it had similar sound hardware, as it used the YM2151, arguably the YM2612's bigger brother, allowing for 8 FM channels (but had no DAC) and two dedicated sample channels.

The MD SSF2 port was terrible. Why it needed to exist I have no idea.