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X-Arcade

X-Arcade

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rallyx.c

0.06 [Nicola Salmoria]


TODO:

- commsega: the first time you kill a soldier, the music stops. When you die, the music restarts and won't stop a second time.

- rallyx: Three things in the schematics that I haven't been able to trace: WR2, WR3 and RDSTB. Only WR3 is actually used by the game.

- rallyx: emulate the explosion with discrete sound components. The schematics are available so it should be possible eventually.

- tactician: the bouncing bomb seems to show incorrect graphics when it's hit.


NOTES:

- The Test Mode "dip switch" actually comes from the edge connector, but is mapped in memory in place of dip switch #8. Dip switch #8 is supposed to freeze the game and is entirely handled by hardware.

- PROM 7a controls the video shape. This is used to hide the rightmost 4 char columns in Locomotion and Commando, while showing them in Jungler and Tactician.

- The playfield scroll registers used in Rally X are present, but not useful (always 0) in Jungler and Tactician. They were removed in Locomotn and Commando.

- commsega has more sprites and more "bullets" than the other games.

- it seems that Jungler doesn't support high priority tiles. Maybe they disabled that feature because they needed more color combinations.

- there are also 1-pixel sprite and bullet placement differences from game to game.

- cottong is a bootleg of a very different version of locomotn, possibly a prototype.

- commsega: Due to a bug at 0x1259, bit 3 of DSW1 also affects the "Bonus Life" value: when bit 3 is OFF, you get an extra life at 30000 pointsand when bit 3 is ON , you get an extra life at 50000 points. At 0x0050 there is code to give infinite lives for player 1 when bit 3 of DSW0 is ON. I can't tell however when it is supposed to be called.


VIDEO HARDWARE NOTES:

- The video mixer of this hardware is peculiar.

- There are two 16-colors palette banks: the first is used for characters and sprites, the second for "bullets".

- When a bullet is on screen, it selects the second palette bank and replaces the bottom 2 bits of the tile palette entry with its own, while leaving the other 2 bits untouched. Therefore, in theory a bullet could have 4 different colors depending on the color of the background it is drawn over; but none of the games use this peculiarity, since the bullet palette is just the same colors repeated four time. This is NOT emulated.

- When there is a sprite under the bullet, the palette bank is changed, but the palette entry number is NOT changed; therefore, the sprite pixels that are covered by the bullet just change bank. This is emulated by first drawing the bullets normally, then drawing the sprites (with pdrawgfx so they are not drawn over high priority tiles), then drawing the pullets again in TRANSPARENCY_PEN_TABLE mode, so that bullets not covered by sprites remain the same while the others alter the sprite color.

- The tile/sprite priority is controlled by the top bit of the tile color code. This feature seems to be disabled in Jungler, probably because that game needs more color combination to render its graphics.


WIP:

- 0.93: Added audio RC_Filter.

- 0.79u1: Merged locomotn.c with rallyx.c driver. Changed palettesize from 32 to 96 colors.

- 0.27: Added locomotn.c driver.

- 0.06: Added rallyx.c driver.