Catalogue of Arcade Emulation Software - the Absolute Reference

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0.34b4 [Ernesto Corvi]


- The main 6502 cpu is a custom one. The differences with a regular 6502 is as follows: Extra opcode ( $4b00 ), wich i think reads an external port. VBlank irq is on bit 1 ( 0x02 ). Reset, IRQ and NMI vectors are moved. Also, there was some protection circuitry which is now emulated.

- The way i dealt with the custom opcode was to change it to return memory position $ff (wich i verified is not used by the game). And i hacked in a read handler wich returns the vblank on bit 1. It's an ugly hack, but works fine.

- The bootleg version patched the rom to get rid of the extra opcode ( bootlegs used a regular 6502 ), the vectors hardcoded in place, and also had the protection cracked.

- The background tiles had a very ugly encoding. It was so ugly that our decode gfx routine will not be able to decode it without some little help. So thats why exprraid_gfx_expand() is there. Many thanks to Phil Stroffolino, who figured out the encoding.

- The Bootlegs: 1st bootleg set expects to read vblank status from 0x3800, country warning sign has been defaced by the bootleggers. 2nd bootleg set expects to read vblank status from 0xFFC0, country warning sign is intact, however Credit is spelt incorrectly.

- 0.34b4: Added exprraid.c driver.