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Package SDIP64
First use 1990 ?
Used on MV4 Cartridges...

PRO-CT0 (also known as SNK-9201 and ALPHA-8921) is an early gate array chip which serializes sprite graphics in AES cartridges and MVS boards. It was later replaced by NEO-ZMC2 and then NEO-CMC.

It was also used as a challenge-response "security" device in Super Sidekicks and Fatal Fury 2 cartridges.

ALPHA-8921 was the original chip name, from when Alpha Denshi were using it on their Alpha68k system.


Sprite graphics mux Security device
Info by User:Kyuusaku
  • D0~D15: 68k data bus
  • A1~A19: 68k address bus
  • D0out~D7out: output to a LS245 which puts the data on

the 68k bus when /PORTOEL goes low ($200000-$2FFFFF odd byte read).

Internal logic

Kyuusaku's Verilog definition:

furrtek's version:

Normal use: graphics multiplexer


Derivate use: security device

PRO-CT0 9042KX023 on an AES cart PROG board.
File:Crt snk-9201.jpg
SNK-9201 chip found in a Super Sidekicks MVS cartridge. Picture courtesy of [MVS-Scans].

As a security device, the chip is only found on PROG-G2 boards for Fatal Fury 2 and Super Sidekicks. It was SNK's first attempt at copy-protecting NeoGeo games.

The chip is tied to the 68k address and data bus, it reacts to word writes and replies on odd addresses in the $200000-$2FFFFF address range.

The game program expects the chip to reply with specific data depending on the values written to it. If the values don't match, then the game assumes it's a copy and silently sets a flag which triggers deliberate bugs during gameplay (see game pages for details).


Address bus mapping:

A19 A18 A17 A16 A15 A14 A13 A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 /PORTWEL A1
C31 C29 C27 C25 C30 C28 C26 C24 C23 C21 C19 C17 C22 C20 C18 C16 H EVEN 12M LOAD

Data bus mapping:

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
C15 C13 C11 C9 C14 C12 C10 C8 C7 C5 C3 C1 C6 C4 C2 C0


Data bus mapping:

D7 D6 D5 D4 D3 D2 D1 D0


MAME simply uses a list of hardcoded values since the games always use the same challenges. See /src/devices/bus/neogeo/prot_fatfury2.cpp