Quickly checked out EarthBound:

C0A11E: A9 30 LDA #$30
C0A120: 8F F0 7F 30 STA $307ff0
C0A124: 1A INA
C0A125: 8F F0 7F 31 STA $317ff0
C0A129: CF F0 7F 30 CMP $307ff0
C0A12D: F0 0C BEQ c0a13b ($c) ;if not equal, copy protection failed

Tries to check a SRAM mirror in there, and, again, I don't know the mumbo-jumbo of SNES mappers, so leave it to Eta ...

[Linked Image from mamedev.emulab.it]