Firstly you need the SMW ROM without a header, and should expand the ROM to 8Mbits using Lunar Expand or with a Hex Editor. The cheats effect that we will be coding is rather extensive. When you grab a coin instead of increasing the coin count it: gives you 99 lives, set the timer to 999, gives you the Cape and sets the item reserve box to contain the Fire Flower.
Since every coin (including Yoshi coins) triggers the cheat, that means that the coin you get at the end when you pass through the end-of-level gate will set your time to 999, meaning you automatically complete the level with an impossibly high time. Since the total time you beat a level in adds to your game's score, it means you can easily get record-breaking scores.
This patch has been tested on a UFO Super Drive Pro 8 (an SNES copier) and has been verified work properly even on a real SNES.
lorom ;set Kxas to lo-rom mapping ORG $808F25 ; coin-handling programming starts here CLC ; clears the carry bit, but is needed as a one-byte command with little overall effect, ; to make sure the desired command lines up on the correct byte CLC ; as the normal coin-handling code I'm replacing is exactly 6bytes long, ; thus 2 CLCs and then the JMP command which in total also occupies 6bytes JMP $908000 ; goes to the code I've added in the expanded part of the rom ORG $908000 ; cheat programming starts here LDA #$09 ; put the number 9 in the accumulator STA $0F31 ; put the accumulator value 9 in the timer's 100s digit STA $0F32 ; put the accumulator value 9 in the timer's 10s digit STA $0F33 ; put the accumulator value 9 in the timer's 1s digit LDA #$02 ; put the number 2 in the accumulator STA $0019 ; put the accumulator value 2 in the memory location for currently active item, and 2 corresponds to the cape STA $0DC2 ; put the accumulator value 2 in the memory location for currently reserve item, and 2 corresponds to the Fire Flower here LDA #$63 ; put the number 99 in the accumulator STA $0DBE ; put the accumulator value 99 in the memory location for current number of lives JMP $808F2B ; go back to the next line in the game's main code, so game can continue