FF4 SNES SRM Checksum

The disassembly I posted before was made by me. I posted the full notes I have but if anyone has any FFIV disassembly I would be happy to get a copy.

I use bsnes+ for breakpoints, geiger's disassembler is also awesome but I'm using Mac Os X. I have a home made disassembler for auto generating the assembly code.

I took a look at $41, it is reset in two places at least:

Code:

$15c9ce when the game starts, I think this is where the RAM is cleared.
$018cb8 when a menu is opened (when loading opens and when main menu is opened)

I don't know what it does but I'm suspecting it's a high byte of $40, $40 is being reset all the time in the entry routine. I think it serves as some sort of deep game timer.

I think $41 (and maybe $40 aswell) is stored in the SRAM somewhere since the value is variable. Maybe next to the game timer?

This is all a lot of guesswork at the moment for me, I'll try to look into this later on.

Rough disassembly of the entry point for FFIV:

Code:

008000     20 2C 80     JSR $802C
008003     6B         RTL 
008004     20 1A BA     JSR $BA1A
008007     6B         RTL 
008008     20 BF C2     JSR $C2BF
00800B     6B         RTL 
00800C     20 92 95     JSR $9592
00800F     6B         RTL 
008010     20 5E 80     JSR $805E
008013     6B         RTL 
008014     20 95 CC     JSR $CC95
008017     6B         RTL 
008018     20 1A BA     JSR $BA1A
00801B     6B         RTL 
00801C     20 BB 82     JSR $82BB
00801F     6B         RTL 
008020     20 92 D7     JSR $D792
008023     6B         RTL 
008024     20 95 CC     JSR $CC95
008027     6B         RTL 
008028     20 6E 80     JSR $806E
00802B     6B         RTL 

00802C     8B         PHB 
00802D     0B         PHD 
00802E     7B         TDC 
00802F     8F 00 41 00     STA $004100.l
008033     A9 7E         LDA #$7E
008035     48         PHA 
008036     AB         PLB 
008037     20 45 80     JSR $8045
00803A     A9 80         LDA #$80
00803C     8F 00 21 00     STA $002100.l
008040     7B         TDC 
008041     EB         XBA 
008042     2B         PLD 
008043     AB         PLB 
008044     60         RTS 

008045     20 3A 87     JSR $873A
008048     20 7D 8C     JSR $8C7D
00804B     BA         TSX 
00804C     CA         DEX 
00804D     CA         DEX 
00804E     8E 65 1A     STX $1A65.w
008051     20 FB 87     JSR $87FB
008054     20 7E 94     JSR $947E
008057     4C 3F 87     JMP $873F
00805A     5C 00 80 03     JML $038000
00805E     48         PHA 
00805F     A9 00         LDA #$00
008061     8F 40 01 00     STA $000140.l
008065     22 03 FD 14     JSL $14FD03
008069     A9 00         LDA #$00
00806B     EB         XBA 
00806C     68         PLA 
00806D     60         RTS 

@assasin: Sounds right, different way to compute the same checksum. Your math impresses me.