Information regarding specific arcade ROMS.

tempest (MAME ROM: tempest) (version 3)<P>
<UL>
<LI>credit counter memory: 0x06 (and 0x16, though this addresses purpose is unknown)
</UL>

tapper (Budweiser, set 1) (MAME ROM: tapper)<P>
<UL>
<LI>overriding rom checksums: edit tappg3.bin change offset 0x0D86 from 0x28 (jump if zero) to 0x18 (unconditional jump)
</UL>

ikari warriors (US JAMMA) (MAME ROM: ikari)<P>
<UL>
<LI>removing ROM checks: edit rom 1.rom change offset 0x0E51 from 0x94 to 0xA0 and offset 0X0E52 from 0x11 to 0x19
<LI>credit counter memory address: 0xFC5C
<LI>credit counter system initialization: occurs at instruction at address 0x00D0 (ld ($F5FC),a -> 0x32 0x5C 0xFC) 
</UL>

ikari warriors (US non-JAMMA with continues) (MAME ROM: ikaria)<P>
<UL>
<LI>removing ROM checks: unnecessary, game will not lock up if ROM check fails
<LI>credit counter memory address: 0xFC5C
<LI>credit counter system initialization: occurs at instruction at address 0x00C8 (ld ($FC5C),a -> 0x32 0x5C 0xFC
<LI>game start credit decrement: at address 0x0A3D (sub $01 -> 0xD6 0x01)
<LI>coin slot 1 credit increment: at address 0x09B7 (add a,(hl) -> 0x86)
<LI>coin slot 2 credit increment: at address 0x09F6 (add a,(hl) -> 0x86)
<LI>Memory Locations 0xFFC0-0xFFFF seem to map to video RAM in character sized tiles, uppercase ascii values map to their respective characters. 0xFF is a solid black tile. The character decorations seem to change during game play though.
</UL>