NEO-SMA



Info from [MAME's source]

QFP144 chip found connected to the P ROMs in some King of Fighters 99, King of Fighters 2000, Metal Slug 3 and in all (?) Garou MVS MotW cartridges. Bankswitches the second megabyte ($200000~$2FFFFF) of P ROM space and provides a 16bit pseudo random number generator.

Upon system reset, the PRN is initialized to $2345.

The chip always (?) replies $9A37 on reads.

=PRN=

16bit LSFR with taps at bits 2,3,5,6,7,11,12,15. Each read steps the register.



=Bankswitching=

Bankswitching is done by unscrambling the written bank number and using a 64 entry (256 bytes) lookup table to map the P ROM into $200000~$2FFFFF.

KOF 99



 * Bankswitching write at $2FFFF1
 * Read chip presence at $2FE447
 * PRN at $2FFFF8 and $2FFFFA

Bankswitch LUT (P2 ROM address):

Garou

 * Bankswitching write at $2FFFC0
 * Read chip presence at $2FE447
 * PRN at $2FFFCC and $2FFFF0

Metal Slug 3



 * Bankswitching write at $2FFFE5
 * Read chip presence at $2FE447
 * PRN at $2FFFF8 and $2FFFFA

Bankswitch LUT (P2 ROM address):

KOF 2000



 * Bankswitching write at $2FFFED
 * Read chip presence at $2FE447
 * PRN at $2FFFD8 and $2FFFDA

Bankswitch LUT (P2 ROM address):