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Catalogue of Arcade Emulation Software - the Absolute Reference

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X-Arcade

X-Arcade

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segaybd.c

0.94 [Aaron Giles]

0.88u3 [Aaron Giles, David Haywood]


TODO:

- Still seems to be some glitchiness in the games in general


NOTES:

- Hardware: Sega Y-board (ew design, with two sprite planes and no tilemaps. The back sprite plane has a huge fillrate and the capability to have its frame buffer completely rotated. Also, it has a palette indirection capability to allows for easier palette rotations. The front sprite plane is System 16b).


WIP:

- 0.113u4: Fixed crash in System 16 games (machinesegaic16.c).

- 0.113u2: Zsolt Vasvari updated a number of Sega games to use the new video timing code.

- 0.108: Brian Troha added more extensive documentation to several of the Sega 16-bit drivers.

- 0.107u2: Massive cleanup/fixing of 16-bit Sega drivers [AWJ]: Many corrections to descriptive set names, adding revision letters, cabinet types, etc. Fixed many dipswitches and added PORT_DIPLOCATION support. Adjusted min/max values for analog controls to improve response. Cleaned up a number of ROM names and fixed some incorrect guesses. Actually disabling 8751 in games that have a fake replacement. Hooked up 8255 PPI correctly now that it has mode 2 support. Fixed behavior of NMI line in later sega sound boards. Fixed addressing in the SegaPCM sound system. Some hardware/documentation cleanup.

- 0.105: Aaron Giles fixed crash in System 16 games introduced by last update.

- 0.104u8: Andre Hufschmidt added save state support to the segaybd.c based games.

- 0.94u2: Aaron Giles fixed CPU speeds according to schematics, hooked up global mute and reduced interleave on all games. Implemented Y-board sprite priorities (not fully understood, but seems to work).

- 10th March 2005: Aaron Giles - I've been looking at is the Y-board sprite priorities. It is clear from the schematics that they hacked in a 7-bit priority value for the line sprites (top layer). Unfortunately, those 7 bits go into a black box custom part that does the mixing with the 16 bits of fancy Y-board rotato-sprites, so a lot of guessing was involved. What makes it even harder is that for the most part, the games make very little use of the priority. It is mainly used for your ship in Galaxy Force 2 and for some of the zoom in/zoom out effects in G-Loc and Strike Fighter. I don't have a full explanation of what the 7 bits of priority do, but I have something that seems to be mostly correct. A baffling aside in this instance. I was searching for cases where the priority was being used and found that it was used in the static title screen on Strike Fighter. What's really bizarre is that periodically during attract mode, the title screen will play some missile sounds and explosions. Well, underneath the title screen, there is actually some graphics animating missiles and explosions, but all of that is over-rendered by the title screen. Even more confusing is that as far as I can tell, this is entirely deliberate. Both the title screen and the missile/explosion sprites are drawn with the fancy Y-board sprite generator, where the priorities don't matter. And even if they did, the title screen is quite clearly higher priority than everything else. If someone knows where to observe a real Strike Fighter, I would be immensely curious to confirm my suspicions.

- 0.94: Changed yboard.c to segaybd.c driver. Aaron Giles updated the Sega 'Y-board' driver which is capable of running Power Drift and Galaxy Force II at full speed in all their rotating glory providing you have a fast enough processor (around 2.5ghz should do it for the most part).

- 4th March 2005: Aaron Giles - Made some good progress on the Y board games. They're all running mostly glitch free with full sprites and rotation working. Speed wise they mostly run 100% on my laptop (2GHz Centrino), except for Galaxy Force 2 which is just insane in parts. Sound is working, but the banking isn't correct yet. R. Belmont has given me a few hints there. Should be able to finish up this weekend I hope!

- 1st March 2005: Aaron Giles - I took a look at Y-board last night. I took apart Haze's skeleton driver and reassembled it in the style of my other Sega drivers. Everything is back together and running as well as it was in 0.93: that is, I can see the System 16B-style sprites. A couple more hours communing with the code and I should hopefully have the Y-board sprites going, thanks to OG's guidance. Then it's on to the rotation chip, which definitely looks like an interesting beast to understand.

- 0.89u3: Aaron Giles created a new machine/segaic16.c to hold non-video common hardware, preliminary multiply/compare implementation moved there and changed segaic_init_palette to take a number of palette entries.

- 0.89u2: Swapped gfx1 roms with gfx2 and changed palettesize to 49152 colors.

- 3rd December 2004: David Haywood readded some basic gfx in yboard based on Aaron's new code.

- 0.88u3: Added yboard.c driver.