NEO-CMC
The most "basic" information published can be found at [MAME:neocrypt.c]
Bellow the detailed information:
The NEO-CMC Chip is a Asic (Application Specific Integrated Circuit). This device can be programmed only once. Usually its a time consuming to design a custom chip directly, because this severals try to use FPGA (Field Programmable Gate Array) before of that. The Asic could be considered a final step from this process where many trials has been performed.
To get a intuition about costs related, please read this: [FPGA vs ASICs production and design]
SNK had planned to put protections to avoid NeoGeo piracy using the NEOCMC algorithm on the PCB NEO-MVS CHAFIO.
This chip is a Toshiba Asic TC190G Series developed between 1990 and 1994. (TODO: include Datasheet) The evolution of this series can be found at [Toshiba Technology RoadMap].
The series TC190G cannot be found in datasheets anymore, but in past years had these models:
- TC190G06CF7008
- TC190G06CF7042
- TC190G06CF7050
and more...
Inside this Custom Chip, SNK put the following Chip designs together:
- NEO-ZMC
- NEO-273
- New scrambling system that interlaces M1 + (CX + S1) to decrypt all the Cartridge ROM data in real time.
The first released PCB with this Asic was NEO-CMC42 on the following cartridges:
| CART ID | TITLE NAME |
| 070 | Zupapa |
| 251 | King Of Fighters 99 |
| 252 | Ganryu |
| 253 | Garou Mark Of the Wolves |
| 254 | Strikers 1945 |
| 255 | Prehistoric Isle 2 |
| 256 | Metal Slug 3 |
| 259 | Bang Bead |
| 260 | Nightmare in the Dark |
| 261 | Sengoku 3 |
On this version only S1 and CRoms were encrypted and M1 remained unencrypted. One year later SNK decided release one more layer on the algorithm, to encrypt M1 also on this mixer chip. Releasing the second model NEO-CMC50 on the following cartridges:
| CART ID | TITLE NAME |
| 008 | Jockey Grand Prix |
| 257 | King Of Figthers 2000 |
| 262 | King Of Figthers 2001 |
| 263 | Metal Slug 4 |
| 264 | Rage of the Dragons |
| 265 | King Of Fighters 2002 |
| 266 | Power Instinct - Matrimele |
| 267 | Pochi to Nyaa |
| 268 | Metal Slug 5 |
| 269 | SNK vs Capcom Chaos |
| 270 | Samurai Showdown Zero / Samurai Showdown 5 |
| 271 | King of Fighters 2003 |
| 272 | Samurai Showdown Zero Special / Samurai Showdown 5 Special |
Some peoples talk about Jockey Grand Prix not be a official game, but it´s not all true. At least it's production was official, because was used the real encryption on that board. That encryption cannot be mocked so easily and only the Toshiba and SNK knew the encryption.
Until today, nobody has released one card using in piracy market using the real chip. That explained why several M1 Rom release over the web wasn't correct until Andreas create a mathematical algorithm that can only half decrypt M1 not totally. Cause totally must be include more controls and keys that only in possession of the hardware can be figured out.
Explanation Later!
Neo-CMC only have two series and can only be found in original cartridges encrypted as listed above.
Pinout
Notes:
- C_e_D[0-15]: C1/C3/C5/C7 data bus
- C_o_D[0-15]: C2/C4/C6/C8 data bus
- CX A[0-21]: C1/C2/C3/C4/C5/C6/C7/C8 address bus
- Pins 87,88 contains a RC circuit clock driver like in a 8085 with X1 and X2 pinouts
- Pins 89 and 92 are short circuited in Cartridge board.