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SRAM Expansion Patch (32Kb)

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Status
Tissue-aware
SRAM Expansion
by madsiur
version 1.0
released on 05/25/2018
apply to headerless FF3us 1.0 ROM
wiki entry
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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.


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
                   $337F08 = fixed value #$E41B (slot 1)
                   $337F0A = fixed value #$E41B (slot 2)
                   $337F0C = fixed value #$E41B (slot 3)
                   $337F0E = fixed value #$E41B (slot 4, useless..)
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[-] The following 7 users say Thank You to madsiur for this post:
  • Gi Nattak (05-25-2018), JWhiteLXXXIX (06-03-2019), NPCnextdoor (07-07-2018), Robo Jesus (06-04-2018), SSJ Rick (05-25-2018), Tenkarider (05-25-2018), Warrax (05-25-2018)



Messages In This Thread
SRAM Expansion Patch (32Kb) - by madsiur - 05-25-2018, 01:33 AM
RE: SRAM Expansion Patch (32Kb) - by madsiur - 10-04-2018, 01:46 AM
RE: SRAM Expansion Patch (32Kb) - by J92R - 01-03-2019, 12:01 PM
RE: SRAM Expansion Patch (32Kb) - by Imzogelmo - 06-03-2019, 11:51 AM
RE: SRAM Expansion Patch (32Kb) - by madsiur - 06-03-2019, 06:07 PM
RE: SRAM Expansion Patch (32Kb) - by Imzogelmo - 06-05-2019, 08:22 AM
RE: SRAM Expansion Patch (32Kb) - by madsiur - 06-08-2019, 08:14 AM

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