Final Fantasy III: FF3us SRAM Expansion

This hack expand SRAM by $1600 bytes for each save slot, allowing now 8Kb for each
save slot plus a 4th 8Kb for general purpose, for a total of 32Kb of SRAM instead of 8Kb. (see readme for all info).

FF3us SRAM Expansion
by madsiur
version 2.0
released on 06/25/2024
------------------------------------------------------------------------------
Files included

sram_nh.ips: patch for FF3us 1.0 headerless ROM.
sram_nh_reverse.ips: reverse patch.
sram.asm: Assembly file to assemble with bass.
------------------------------------------------------------------------------
Offset changed, free space used (by patch)

$C0FFD8: Internal header SRAM size (from $03 to $05)
Bank $C3: A few offsets related to saving and loading (see asm file)
$C3F091: $92 bytes of free space
------------------------------------------------------------------------------
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 for 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.
------------------------------------------------------------------------------
Version history

06/24/2024 2.0 release
-fixed hack breaking bug where extra SRAM for slots 1 and 2 would not be loaded in $336000 at game loading
-changed most of saving/loading code to use less free space

10/04/2018 1.1 release
-removed $336000 init (see sram.asm for details)
-renamed $337F08-$337F0E from "fixed value" to "checksum value"

05/25/2018 1.0 initial released
------------------------------------------------------------------------------
Alternate downloads

https://www.fred65816.net/en/romhacking/hacks/sram
https://www.ff6hacking.com/wiki/doku.php?id=ff3:ff3us:patches:madsiur:sram
------------------------------------------------------------------------------
Contact

themadsiur@gmail.com


File: Final Fantasy III (U) (V1.0) [!].smc
CRC32: D184D919
MD5: 4CDFC79B44CD6D532DC6631A5C762094
SHA1: 258BCBC5B7BCC25098BF598C4FF2AA6AC00FDE16