I've been poking around with the idea of disassembling Rockman Megaworld to see what makes it tick with a view to making a hack of it which improves its faithfulness to the NES originals and/or splitting the games off as independent games of their own. I've not got much, but I do know it has a ker-razy checksum routine. Dig this: Code (ASM): loc_354: lea (ROM_Start).w,a0 lea (unk_200).w,a1 moveq #$F,d2 ; run checksum check sixteen times moveq #$FFFFFFFF,d1 loc_360: moveq #0,d0 loc_362: add.w (a0)+,d0 dbf d1,loc_362 cmp.w (a1)+,d0 bne.s BadChecksum dbf d2,loc_360 At $200 there's a list of checksums: Code (ASM): unk_200: dc.w $5648 dc.w $6B30 dc.w $5F4A dc.w $D70C dc.w $256E dc.w $F9FE dc.w $C0AF dc.w $B38A dc.w $01B7 dc.w $236D dc.w $10B2 dc.w $0E51 dc.w $A5EA dc.w $0EAF dc.w $6519 dc.w $9C66 dc.w $7A4D dc.w $4FF9 dc.w $00FF dc.w $0414 As far as I can tell this checksums everything from $0 to $FFFFF, but in sixteen chunks ($0 to $FFFF, $10000 to $1FFFF, $20000 to $2FFFF etc). BadChecksum writes to some VDP registers, then does the familiar red-screen-of-death. Does anyone have any work on this game, or know of anyone who's done any work on this game?