SRAM Expansion
Patch data
| Name | SRAM Expansion 2.0 |
| Author | madsiur |
| Link | Download |
Rom data
| ROM Name | Final Fantasy III (USA) 1.0 |
| ROM SHA-1 | 4F37E4274AC3B2EA1BEDB08AA149D8FC5BB676E7 |
| Header | No |
Offsets
| $C0FFD8 | Internal header SRAM size (from $03 to $05) |
| Bank $C3 | A few offsets related to saving and loading (see asm file) |
| $C3F091-$C3F122 | Extra code (see asm file) |
New SRAM map
Slot 1 expansion: $306A00-$307FFF
$306000-$3069FF = $7E1600-$7E1FFF
Slot 2 expansion: $316A00-$317FFF
$316000-$3169FF = $7E1600-$7E1FFF
Slot 3 expansion: $326A00-$327FFF
$326000-$3269FF = $7E1600-$7E1FFF
Other SRAM values: $336000-$3375FF (game common SRAM)
$337600-$337EFF (unused)
$337F00 = last altered savefile
$337F01 = rng index
$337F08 = checksum value #$E41B (slot 1)
$337F0A = checksum value #$E41B (slot 2)
$337F0C = checksum value #$E41B (slot 3)
$337F0E = checksum value #$E41B (slot 4)
Description
This hack expands SRAM by $1600 bytes, allowing now $2000 bytes for each save slot plus a third 8Kb for general purpose. In original game, only 8Kb of SRAM is used ($306000-$307FFF), each slot occupying $0A00 bytes and $200 bytes for general purpose at the end of the 8Kb block.
With this hack, $306000-$307FFF is used for slot 1, $316000-$317FFF for slot 2 and $326000-$327FFF for slot 3. $336000-$337FFF is used for game SRAM as well. When you play the game, $7E1600-$7E1FFF is still used and copied to correct slot at saving. $336000-$3375FF is copied to correct slot as extra SRAM. At game loading, correct slot is loaded into $336000-$3375FF. So in order to save or load from extra SRAM in your hack, use as an example STA $336000,X or LDA $336000,X.
Since $337600-$337EFF is not used, it means it could be used as scratchpad RAM for temporary things or have a general use common to the three slots.
SRAM could be expanded more but I figured a whole $2000 bytes instead of $0A00 is enough expansion for any hack. In HiROM mapping banks $20-$3F can be used to map SRAM, using always the $6000-$7FFF range of the bank. $C0FFD8 tell the emulator the SRAM size of the ROM.
I have not tested this on sd2snes, Everdrive or real hardware. snes9x 1.55 and bsnes+ were used for testing. If you plan to use this hack and make a cart of your hack after, I have no idea what kind of cartridge you will need or if 32Kb of SRAM is supported by any existing SNES game.