SNK-9201
Protection chip in SDIP64 package used in MVS cartridges. It is found in Fatal Fury 2 and Super Sidekicks only. Some other games use PROG boards that support the chip, but did not include it. No decryption or banking. It was the first attempt at protecting NeoGeo games.
The chip is mapped into the 68k address space ($200000-$2FFFFF) and various values are written to it to various addresses. The game program expects the chip to reply with specific data depending on the values written and will freeze if the wrong values are returned.
Emulation
MAME emulation (fatfury2_protection): [[1]]