~~NOTOC~~
===== SRAM Expansion =====

[[ff3:ff3us:patches:madsiur|{{ff3:ff3us:patches:madsiur:madbutton.png}}]]

==== Patch data ====

|Name               |SRAM Expansion 1.1 |
|Author             |madsiur  |
|Link               |{{ff3:ff3us:patches:madsiur:sram.zip|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) |
| $EFFBC8-$EFFC16 | Extra code (see asm file) |

==== SRAM map ====
<code>
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, useless..)
</code>

==== Description ====

This hack expand SRAM by $1600 bytes for each save slot, allowing now 8Kb bytes for each save slot plus a third 8Kb for general purpose for a total of 32Kb of SRAM. 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. 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 and $7E1600-$7E1FFF. 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 use as scratchpad SRAM for temporary things or have a general use common to the three slots. $337FF0-$337FFF has same function as the original $307FF0-$307FFF.\\

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, you will need a HiROM cart with a 32Kb memory chip. I have no idea if any existing SNES game has already 32Kb of SRAM.\\

==== Links ====

[[http://www.ff6hacking.com/forums/showthread.php?tid=3694|Forum Thread]]\\